Bivalia Orders
1. Anterior and posterior later teeth prsent on inside of valves. . . . . . . . . Veneroida, 2
Anterior pseudodardinal tooth and posterior lateral tooth present on valves. Unionoida, 7
Veneroida Families/Species:
2. Shell hinge external; hinge teeth present or absent; shell not triangular in cross section. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Shell hinge internal; hinge teeth absent; shell triangular in cross section; stripesLateral teeth serrate; externaloften present on exterior of shell. . . Dreissenidae, Dreissenia, 4
3. Lateral teeth serrate; external surface with raised concentric ridges; thick shell yellow to brown, often with a purple stripe on umbo; adults generally >2.5 cm. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Corbiculidae, Corbicula fluminea
Lateral teeth smooth; external shell smooth or with fine, concententric striae; thin shell; adults generally <2.5 cm. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sphaeriidae, 5
4. Shell vntral margin flat to concave and flattened; ventrolateral shouylder with a ridge; shell triangular in cross section; variable colors but often with prominent stripes; zebra mussel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dreissenia polymorpha
Shell ventral margin rounded, convex, never flattened; ventrolateral shoulder without a ridge; color pale (especially near hinge) but may have dark concentric rings; guagga mussel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dreissenia rostriformis bugensis
5. Umbo anterior. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Umbo distinctly posterior. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pistium sp.
6. Two cardinal teeth in one valve and one in opposiing valve; shell not mottled. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sphaerium/Musculium sp.
Unionoida Families/Species:
7. Hinge without teeth, but hinge may be thickened . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Hinge with distinct teeth. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
8. Umbos flush with dorsal margin or nearly so. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Umbos projecting above dorsal margin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
9. Shell quite circular in profile, nearly as high as long. . Utterbackiana suborbiculata
Shell noticeably elongate, much longer than high. . . . . . . . . . . . . . . . . . . . . . . . . . . 10
10. Umbos barely rising above dorsal margin, with green rays, rudimentary teeth. . . . 11
Umbos flush with dorsal margin, with vague green or yellowish unbroken rays, no teeth. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . Utterbackia imbecillis
11. Rays bold, broken; umbo more than 25% of the total length from the anterior margin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hemistena lata*
Rays distinct but not bold; umbo in anterior 25% of shell . . . . . . Leptodea leptodon*
12. Double-looped beak sculpture, at least initially 7 6b Concentric beak sculpture. . . . 13
Concentric beak sculpture. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
13. Beak sculpture initially double-looped, becoming a series of zig-zag lines. . . . . . . . 14
Beak sculpture entirely double-looped. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
14. Beak sculpture fine, ribs crowded together and separated by less than their width. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pyganodon lacustris*
Beak sculpture coarse, ribs separated by more than their width. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pyganodon cataracta marginata*
15. Each rib of beak sculpture uniformly strong along its length, not nodulose; umbo in 25% anterior of shell. . . . . . . . . . . . . . . . . . . . . . Pyganodon cataracta marginata*
Each rib of beak sculpture most developed at bottom (distal) of each loop, often nodulose, umbo in 25% to 33% anterior of shell. . . . . . . . . .. . . . . . . . . Pyganodon grandis s.1.
16. Shell brownish or gray, rayless, with small, indistinct teeth Simpsonaias ambigua (p. 288). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Simponaias ambigua
Shell brown, yellow or greenish, often with rays; hinge may gently "S"-shaped with no teeth present. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
17. Beak sculpture of fine, concentric loops; shell often elongate and cylindrical; common in extreme headwaters. . . . . . . . . . . . . . . . . . . . . . . . Anodontoides ferussacianus
Beak sculpture of coarse, concentric loops; shell often rather compressed; common throughout most stream reaches. . . . . . . . . . . . . . . . . . . . . . . . Strophitus undulatus
18. Nacre at least partially purple or pinkish purple in anterior 50% of shell (does not include iridescent reflections; shell material itself must be purple). . . . . . . . . . . . . . . . 19
Nacre not purple. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
19. Shell nearly circular in profile, heavily sculptured with pustules; hinge very thick, short. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cyclonaias tuberculata
Shell not as above. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
20. Shell with a distinct wing posterior to the umbo, flattened; OR if wing is absent, dark dorsal slope contrasts with yellow shell disc. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Shell without wing, dorsal slope not contrasting with disc of shell. . . . . . . . . . . . . . . . 23
21. Exterior of shell yellowish, darker toward the umbos; nacre may be purple toward the beak cavities but white or yellow elsewhere. . . . . . . . . . . . . . . . . . Leptodea fragilis*
Shell not as above. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
22. Exterior of shell dark brown, black, or green with distinct rays. . . . Potamilus alatus
Exterior of shell greenish, tan, or gray, shiny; may have a wing anterior to umbo. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Potamilus ohiensis
23. Nacre of shell with minute pits in center portion of shell. . . . . . . . . . . . . . . . . . . . 24
Nacre not pitted. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
24. Shell very elongate with broad, prominent dorsal ridge giving shell a twisted appearance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cumberlandia monodonta*Shell 2 to 3 times as long as high, dorsal ridge low and scarcely perceptible. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Margaritifera margaritifera*
25. Shell less than 2 times as long as high, usually not pointed posteriorly. . . . . . . . . . 26Shell elongate, 2 to 4 times as long as high, pointed posteriorly. . . . . . . . . . . . . . . . . 33
26. Shell highest posterior to umbo, hinge teeth small. . . . . . . . . . . . . . . . . . . . . . . . 27
Shell highest at umbo or equally high with posterior of umbo, often with a “humped” appearance; hinge teeth large or small. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
27. Shell laterally compressed, periostracum silky and rough. . . . Elliptio complanata*
Shell not laterally compressed, periostracum with matte finish or smooth. Villosa lienosa
28. Ventral posterior margin with serrated, wide, raised rib. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Epioblasma obliquata obliquata
Not as above. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
29. Hinge teeth light, often lamellar, hinge long and broadly arched, interdentum absent. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Glebula rotundata*
Hinge teeth heavy, not lamellar, hinge short and angled, interdentum present or absent. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
30. Umbos prominent, shell as high as wide or higher. . . . . . . . . . . . . . . . . . . . . . . . 31
Umbos low, shell obviously longer than high. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
31. Shell as high as long, umbos dorsal. . . . . . . . . . . . . . . . . . . . . Obovaria retusa*
Shell noticeably longer than high, umbo at anterior margin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Epioblasma obliquata obliquata
32. Interdentum wide, thick; shell large as adult. . . . . . . . . . . . . . . Elliptio crassidens
Interdentum narrow or absent; shell small as adult. . . . . . . . . . . . . Toxolasma lividum
33. Shell with indistinct rays or rayless, periostracum dull. . . . . . . . . . Elliptio dilatata
Shell, at least when small, with distinct broad rays; periostracum shiny 28
34. Hinge very weakly developed, laterals absent. . . . . . . . . . . . . . . . . Hemistena lata
Hinge well-developed, laterals present. . . . . . . . . . . . . . . . . . . . . . . . . . Ligumia recta
35. Shell without lateral teeth. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Shell with lateral teeth. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
36. Shell about 1.5 or more times longer than high. . . . . . . . . . . . . . . . . . . . . . . . . . 37
Shell nearly as high as long, quite flattened. . . . . . . . . . . . . . . Lasmigona complanata
37. Shell sculptureless and rayless, usually brownish, gray, or black. . . . . . . . . . . . . . 38
Shell colored with rays and/or possessing corrugations on posterior slope. . . . . . . . . . 40
38. Nacre with minute pits in central portion of shell. . . . . . . . . . . . . . . . . . . . . . . . . 39
Nacre without pits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Simpsonaias ambigua
39. Shell very elongate with broad, prominent dorsal ridge giving shell a twisted appearance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cumberlandia monodonta*
Shell 2 to 3 times as long as high, dorsal ridge low and scarcely perceptible. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Margaritifera margaritifera*
40. Shell less than twice as long as high, chunky, no corrugations on posterior slope. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Alasmidonta viridis
Shell about 1.5 to 2 times as long as high, corrugations present. . . . . . . . . . . . . . . . 41
41. Shell with coarse ribs and corrugations over disc of shell, beak sculpture of 2 rows of heavy knobs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arcidens confragosus*
Not as above. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
42. Corrugations fine, beak sculpture of heavy ribs. . . . . . . . . Alasmidonta marginata
Corrugations heavy, beak sculpture of fine ribs. . . . . . . . . . . . . . . . Lasmigona costata
43. Disc of shell sculptureless or not sculptured as above. . . . . . . . . . . . . . . . . . . . . . 44
Disc of shell predominately sculptured with distinct pustules rather than ribs; largest pustules not arranged in a single row. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
44. Shell with coarse ribs and corrugations over disc of shell, beak sculpture of 2 rows of heavy knobs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arcidens confragosus*
Not as above. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
45. Shell nearly round in profile; sulcus absent or narrow and indistinct, sometimes present only on small specimens. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Shell not as above; sulcus present or replaced by a massive, nodulose rib. . . . . . . . . . 50
46. Shell with broad, green ray or blotch radiating from umbo, which may disappear on mature shell. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cyclonaias pustulosa pustulosa
Shell without ray or with numerous very fine lines. . . . . . . . . . . . . . . . . . . . . . . . . . . 47
47. Disc of shell sculptured with numerous pustules scattered over shell 42 41b Disc of shell sculptured with a few pustules arranged in two indistinct, radiating rows. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cyclonaias nodulata
48. Beak cavity deep, compressed; shell with or without vague rays. . . . . . . . . . . . . . 49
Beak cavity shallow, open; shell with distinct, dotted, numerous rays. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cyprogenia stegaria
49. Posterior slope flattened into a wing with narrow ribs on posterior slope radiating out to shell margin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cyclonaias tuberculata
Posterior slope without wing or with wing very poorly developed; ribs on posterior slope arranged parallel to posterior ridge. . . . . . . . . . . . . . . . . . Plethobasus cooperianus*
50. Shell elongate, at least twice as long as high 45 44b Shell not elongate. . . . . . . . . 51
51. Shell cylindrical, about as wide as high. . . . . . . . Theliderma cylindrica cylindrica
Shell compressed, obviously higher than wide. . . . . . . . . . . . . . . Tritogonia verrucosa
52. Shell with a massive, nodulose rib radiating from umbo to posterior ventral margin, patterned with tent-like markings. . . . . . . . . . . . . . . . . . . . . . Theliderma metanevra
Shell with a sulcus, not patterned as above. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
51. Posterior wing with narrow, well-defined granulose ribs. . . . . . . Quadrula quadrula
Posterior wing with coarse, irregular ribs and large pustules. . . . . . . Quadrula fragosa*
52. Sculpture predominately of a single row of knobs radiating from the umbo to the ventral margin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Sculpture of broad, oblique ribs; pustules may also be present; OR shell is sculptureless. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
53. Knobs large, alternating in position from left to right valves, usually with a corrugated posterior ridge, usually rayed. . . . . . . . . . . . . . . . . . . . . . . . . . . . Obliquaria reflexa
Knobs low, not obviously alternating in position; posterior ridge not corrugated; usually rayless or weakly rayed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
54. Umbos at or before anterior margin, facing forward. . Plethobasus cicatricosus*
Umbos 25% to 33% of the total length behind the anterior margin; umbos face each other. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Plethobasus cyphyus
55. Shell sculptured with broad, oblique ribs; pustules may also be present. . . . . . . . . 56
Shell sculptureless except for growth lines or low rib bounding the sulcus. . . . . . . . . . 57
56. Pustules absent anterior of umbo, hinge massive. . . . . . . Amblema plicata plicata
Pustules occur anterior of umbo, hinge not massive. . . . . . . . . . Megalonaias nervosa
57. Shell oval or nearly circular, umbo central, without a posterior or anterior wing, patternless or with a broad green ray on the umbo. . . . . . . . . . . . . . . . . . . . . . . . . . 58
Shell not as above. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
58. Shell with a broad, green ray or blotch on umbo. Quadrula pustulosa pustulosa*
Shell without green ray. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
59. Hinge heavy; interdentum present. . . . . . . . . . . . . . . . . . . . Obovaria subrotunda
Hinge light; interdentum absent. . . . . . . . . . . . . . . . . . . . . . . . . . Glebula rotundata
60. Shell quite flattened, rounded, plate-like, winged, with heavy “V”-shaped beak sculpture; hinge heavy. . . . . . . . . . . . . . . . . . . . . . . . . . . . Lasmigona complanata
Shell not as above. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
61. Shell elongate, about 2 to 4 times longer than high. . . . . . . . . . . . . . . . . . . . . . .62
Shell shorter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
62. Shell yellowish or tan with distinct green rays. . . . . . . . . . . . . . . . . . . . . . . . . . 63
Shell not as above. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
63. Shell thinner, hinge delicate, interdentum narrow or absent. . . . . . . . . . . . . . . . 69
Shell thick, hinge thick, interdentum wide. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
64. Teeth rudimentary, no beak sculpture. . . . . . . . . . . . . . . . . . . . . Hemistena lata*
Teeth small but well-developed, wavy or “V”-shaped beak sculpture. . . . . . . . . . . . . . 65
65. Shell highest at umbo, posterior point in ventral half of posterior margin, beak sculpture wavy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Villosa iris
Shell highest behind umbo, posterior point in dorsal half of posterior margin, beak sculpture “V”-shaped. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ligumia subrostrata*
66. Rays interrupted, often checkerboard patterned. . . . . . Ptychobranchus fasciolaris
Rays continuous, wavy, narrow. . . . . . . Venustaconcha ellipsiformis ellipsiformis*
67. Shell inflated, pointed posteriorly, with coarse, concentric beak sculpture that opens forward. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Uniomerus tetralasmus
Shell not as above. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
68. Shell dark and/or rayed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Shell waxy yellowish, rayless. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lampsilis teres
69. Beak sculpture of heavy, trapezoidal ribs, indistinctly rayed if at all, laterals heavy, hinge short. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Elliptio dilatata
Shell not as above. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
70. Nacre with minute pits in central portion of shell. . . . . . . . . . . . . . . . . . . . . . . . . 71
Nacre without pits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
71. Shell very elongate with broad, prominent dorsal ridge giving shell a twisted appearance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cumberlandia monodonta*
Shell 2 to 3 times as long as high, dorsal ridge low and scarcely perceptible. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Margaritifera margaritifera*
72. Shell flattened, thin, drawn to pronounced point posteriorly that ends at or above the halfway point between the ventral and dorsal margins; OR posterior point twisted to end below halfway point. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Shell may be cylindrical, thick, posterior more evenly rounded and ending about halfway between ventral and dorsal margins. . . . . . . . . . . . . . . . . . . . . . . . . . . Ligumia recta
73. Shell length less than 2 times the height; posterior point forms an angle greater than 80°. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . Ligumia subrostrata*
Shell length more than 2 times the height; posterior point forms an angle less than 80°. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ligumia nasuta
74. Shell wedge-shaped, triangular, umbo near anterior margin, with wide, green, broken rays. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Shell not as above. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
75. Shell as high as or higher than long, highly polished and waxy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pleurobema bournianum (see Pleurobema clava)
Shell longer than high, rarely waxy and polished. . . . . . . . . . . . . . . Pleurobema clava
76. Umbos either face each other OR are low and turned forward. . . . . . . . . . . . . . . . 77
Umbos prominent and turned forward. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
77. Shell obviously sulcate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
Shell not sulcate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
78. Sulcus bounded posteriorly by low rib or swelling that protrudes past the margin of the shell, causing the margin anterior to this to be concave. . . . . . . . . . . . . . . . . . . . 79
Not as above. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
79. Shell oval or round in profile, concave margin slight; ribs bounding sulcus barely protrude past margin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Epioblasma personata*
Shell not oval or round, concave margin deep; ribs bounding sulcus extend well beyond the margin to form digitations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
80. Rib anterior to sulcus colored dark green distally. . . . . . . . . . Epioblasma lewisi*
Rib anterior to sulcus with fine rays but not darkly colored. . . . Epioblasma flexuosa*
81. Shell yellowish, elongate; may have broad, green, broken rays. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ptychobranchus fasciolaris
Shell not as above. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
82. Shell drawn to a blunt point posteriorly, the point about halfway between dorsal and ventral margins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
Shell rounded posteriorly; OR if drawn to a point, point is near ventral margin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fusconaia flava
83. Sulcus bordered anteriorly by low swellings or prominent knobs delimited by growth lines; sulcus causes a shallow indentation in the shell outline as early as the third year. 84
Sulcus smoothly joins disc of shell, not causing an indentation in the shell outline except in older individuals; outline smoothly rounded. . . . . . Epioblasma obliquata perobliqua
84. Region anterior of sulcus with low swellings. . . . Epioblasma torulosa rangiana*
Region anterior of sulcus with prominent knobs. . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
85. Knobs small, numerous, crowded. . . . . . . . . . . . . . . . . . . Epioblasma philipsii*
Knobs large, few, distantly spaced. . . . . . . . . . . . . . Epioblasma torulosa torulosa*
86. Posterior ridge sharp, concave or straight, shell about as high as long, drawn to a distinct point posteriorly about halfway between the dorsal and ventral margins; umbos facing each other; beak cavities shallow, open. . . . . . . . . . . . . . . . Truncilla truncata
Shell not as above. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
87. Posterior ridge prominent, straight or concave; shell noticeably longer than high, inflated; periostracum satiny if present; posterior slope with numerous fine ridges, chevron markings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Epioblasma triquetra
Shell not as above. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
88. Beak cavity deep, compressed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
Beak cavity shallow, open. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
89. Sulcus absent. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
Sulcus present. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
90. Hinge not massive, cardinal teeth aligned vertically. . . . . . . . . . . . . . . . . . . . . . . 91
Hinge massive, cardinal teeth aligned horizontally. . . . . . . . . . . . . . . . . . . . . . . . . . . 91
91. Umbos prominent, near anterior margin. . . . Fusconaia subrotunda subrotunda
Umbos low, more centrally located. . . . . . . . . . . . . . . . . . . . . . . . . . . Fusconaia flava
92. Juvenile shell rayed. . . . . . . . . . . . . . . . . . . . Fusconaia subrotunda subrotunda
Juvenile shell unrayed except for a yellow ray on the dorsal slope. . . . Reginaia ebenus
93. Cardinal teeth aligned horizontally. . . . . . . . . . . . . . . . . . . . . . . Reginaia ebenus
Cardinal teeth aligned vertically. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
94. Sulcus weak or absent, umbos at or behind anterior margin. . . . . . . . . . . . . . . . . 95
Sulcus well-developed, umbos at or before margin. . . . . . . . . . . . . . . . . . . . . . . . . . 96
95. Shaped like isosceles triangle in profile, umbos prominent. . . Pleurobema plenum*
Not shaped like isosceles triangle, umbos wide and low. . .. . . . . Pleurobema sintoxia
96. Shaped like scalene triangle; umbos before anterior margin; nacre rose or white . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pleurobema rubrum
Not shaped like a scalene triangle; umbos slightly before anterior margin; nacre white. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pleurobema cordatum
97. Cardinal teeth aligned horizontally. . . . . . . . . . . . . . . . . . . . . Obovaria olivaria*
Cardinal teeth aligned vertically. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
98. Sulcus distinct, periostracum satiny. . . . . . . . . . . . . . . . . Pleurobema cordatum
Sulcus absent; OR if present, periostracum not satiny. . . . . . . . . . . . . . . . . . . . . . . . 99
99. Umbos prominent, shell pointed posteriorly. . . . . . . . . . . . Pleurobema sintoxia
Shell not as above. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
100. Shell quadrate; sulcus is usually a flattened area; nacre white or salmon. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fusconaia flava
Shell rounded; sulcus is usually absent; nacre white, pink, or salmon. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pleurobema sintoxia
101. Posterior of shell with a distinct outward swelling beyond margin of shell. . . . . . 102
Posterior of shell without swelling, although posterior of entire shell may be noticeably inflated. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
102. Posterior swelling expansive, not ridged. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
Posterior swelling not greatly expanded beyond the margin, swelling radially ridged. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
103. Region anterior of sulcus with low swellings. . . . . Epioblasma torulosa rangiana
Region anterior of sulcus with prominent knobs. . . . . . . . . . . . . . . . . . . . . . . . . . . 104
104. Knobs small, numerous, crowded. . . . . . . . . . . . . . . . . . . Epioblasma philipsii*
Knobs large, few, distantly spaced. . . . . . . . . . . . . . . Epioblasma torulosa torulosa*
105. Shell nearly round, posterior swelling low and not well developed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Epioblasma personata*
Shell oval or elongate, posterior swelling well developed. . . . . . . . . . . . . . . . . . . . . 106
106. Shell oval, not obviously inflated; beaks not prominent. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Epioblasma obliquata perobliqua
Shell more elongate, very inflated; beaks prominent. . . . . . . . . Epioblasma triquetra
107. Hinge on left valve with a tongue-like tooth under the beak in the interdentum posterior to the cardinal teeth and a small, wing-like extension on the posterior dorsum. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lasmigona compressa
Shell not as above. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
108. Shell thin, inflated, pointed posteriorly, with sharp concentric beak sculpture, the loops facing forward. . . . . . . . . . . . . . . . . . . . . . . . . . . . Uniomerus tetralasmus
Shell not as above. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
109. Shell yellowish, compressed, thick; beaks low; hinge massive, not oval or round in outline. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
Shell not as above. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
110. Shell elongate, with interrupted green rays. . . . . . . . Ptychobranchus fasciolaris
Shell almost as high as long, with narrow rays containing darker, chevron markings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ellipsaria lineolata*
111. Hinge delicate, with small, chunky teeth; nacre may be iridescent; dorsal ridge smoothly rounded. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
Hinge not delicate, teeth more massive; nacre white or flushed with pink, not iridescent or iridescent only posteriorly; dorsal ridge may be sharp. . . . . . . . . . . . . . . . . . . . . . . 116
112. Shell compressed and thin, yellowish with a dark dorsal slope, rayless or with vague green rays. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Leptodea fragilis
Shell not as above. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
113. Shell small (about 1 in.), without rays, quite cylindrical. . . . . Toxolasma parvum
Shell up to 2 in., with rays, compressed to cylindrical. . . . . . . . . . . . . . . . . . . . . . . 114
114. Cardinal teeth chunky, triangular, beak sculpture wavy. . . . . . . . . . . . . Villosa iris
Cardinal teeth lamellar or rudimentary, beak sculpture double-looped or lacking. . . . 115
115. Shell elongate, no beak sculpture. . . . . . . . . . . . . . . . . . . . Leptodea leptodon*
Shell oval, beak sculpture double-looped. . . . . . . . . . . . . Lasmigona subviridis*
116. Shell oval, heavy, yellow or greenish often with broad rays; hinge massive; umbo very low. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
Shell not as above. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
117. Shell abruptly truncated posteriorly. . . . . . . . . . . . . . . . . . . . . Lampsilis abrupta
Shell gently rounded posteriorly. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
118. Shell yellowish, rayless or with vague green rays; umbos in anterior 25% of shell; umbos wide and massive. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lampsilis abrupta*
Shell yellowish, greenish, or brown, usually with well developed greenrays; umbos located 25% or more back from anterior margin, umbos wide but low. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Actinonaias ligamentina s.1.
119. Shell small (less than 2 in.), somewhat elongate, pointed posteriorly. . . . . . . . . 120
Shell may be larger, oval or cylindrical, usually not pointed posteriorly. . . . . . . . . . . 121
120. Shell very thick for its size, with greenish rays; hinge short and thick. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Villosa fabalis
Shell not thick, hinge not as above, shell with rayed or checkerboard pattern of various colors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Truncilla donaciformis
121. Shell noticeably highest at umbo. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
Shell highest posterior to umbo; OR umbo flush with posterior margin. . . . . . . . . . . 125
122. Shell greatly inflated, hinge line gently “S”-shaped. . . . . . . . . . Potamilus capax*
Shell inflated or not; hinge line straight, curved, or angled. . . . . . . . . . . .. . . . . . . . 123
123. Shell oval, chunky, very thick; hinge massive; umbos large. . Ellipsaria lineolata*
Shell not as above. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
124. Dorsal ridge concave, sharp. . . . . . . . . . . . . . . . . . . . . . . . . . . Lampsillis ovata
Dorsal ridge straight or convex, rounded. . . . . . . . . . . . . . . . . . . . . Lampsilis cardium
125. Shell oval, yellowish, with numerous fine, wavy, dark green to brown rays. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lampsilis fasciola
Shell not as above. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
126. Shell pointed posteriorly, inflated, thick, with interrupted rays. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Epioblasma triquetra
Shell not as above. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
127. Shell blackish, not obviously rayed. . . . . . . . . . . . . . . . . . . . . . . . Villosa lienosa
Shell yellowish or greenish, usually rayed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
128. Shell small (about 1 in.), thick, greenish with darker rays; hinge short, thick. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Villosa fabalis
Shell may be larger, not noticeably thick, yellowish; may have widely spaced green or brown rays; hinge not as above. . . . . . . . . . . . . . . . . . . . Lampsilis radiata luteola*
*Not listed by Ohio EPA