1. Birotules and pseudobirotules (see Terms) absent. . . .. . . . . . . . . . . . . . . . 2
Birotules and pseudobirotules present . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2. Microscleres and/or gemmuloscleres present (not . . . . . . . . . . . . . . . . . . . . 3
Microscleres minute birotulates or sterllate. . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Microsclerres straight and with knobbed spines that are longer near center of spicule; gemmoscleres, when present, biotulates of two forms depending upon length, grading into one another; sponge growth flat and encrusting to massive. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Heteromeyenia 4
Microscleres gently curved with microspines of even size distributed over the spicule or microspines absent, gemmoscleres, when present, not birotulates. 5
4. Foraminal tubule with one or two very long tendrils, often enveloping the tubule; megascleres 270 um long, smooth or sparsely microspined; shorter birotulates with rotules bearing deeply cut rays; longer birotulates with a smooth or sparsely microspined shaft, rotules bearing deeply cut rays;usually thin and encrusting in running waters. . . . . . . . . .. . . Heteromeyenia latitenta
Foraminal tubule with three or more tendrils of varying length; megascleres sparsely microspined. Foraminal tubule one-half to once the diameter of the gemmule body, with four to six long tendrils; shorter birotulates 40 um long, with smooth shaft, and with rotules composed of three to five rays; longer biotulataes 60 um long, ususally with a thinner smooth shaft, and with rotules composed of 3-5 rays; megascleres 300 um long; microscleres 90 um long; an encrusting form with soft papillate projections, usually in running waters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Heteromeyenia tubisperma
5. Gemmoscleres amphistrongyla, coursely spined; sponged may be incrusting or massive, often forming free, fingerlike extensions. . . . . . . . . Spongilla lacustris
6. Microscleres stellate. . . . . . . . . . . . . . . . . . . . . . . . . . . . Dosilia radiospiculata
Microscleres birotulate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7. Gemmules and gemmoscleres absent. [The absence of gemmules and gemmoscleres in species lacking microscleres makes accurate identification even to genus nearly impossible. Nontheless, the occasion will arise when it is worthwhile to attempt to categorize specimens as much as possible to guide future study. The followiong selections provide the closest match of various taxa and characteristics of the megasclere.]
A. Megascleres always smooth. . . . . . Eunapius and some Ephydatia populations B. Megascleres smooth to spiny with all degrees of variation. . . . . . . Ephydatia C. Megascleres always spiny.
1. Spines blunt. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Trochospongilla 2. Terminal spines directed toward spicule tips. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Anheteromeyenia and Radiospongilla
Gemmules and gemmoscleres present. . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
8. Gemmules enclosed in a thick yellowish or reddish-brown coat, forming a contiguous layer at base of sponge; gemmocleres not birotulates or true gemmoscleres absent. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Eunapius fragilis
Gemmules not enclosed in coat, scattered throughout sponge . . . . . . . . . . . 9
9. Spines of megascleres, viewed under high magnification, with blunt spiny tips or crowns; rotules of gemmoscleres with entire margins not excised to form serraations or spines. . . . . . . . . . . . . . . . . . . . . . . . . . . Trochospongilla, 10
Spines of megascleres pointed; rotules of gemmosccleres with serrated or spiny (rayed) margins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
10. Megascleres with spines , which viewed under high magnification, have blunt spiny tips or crowns; rotules of gemmoscleres with entire margins, not excised to form serrations or spines. . . . . Trochospongilla leidyi or T. pennsylvania, 11
Megascleres not spined; gemmules formed in a basal layer; color grayish or drab. . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Trochospongilla leidyi
11. Gemmosclere rotules normally strongly unequal in diameter, on average gemmosclere length greater or equal to diameter of rotules. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Trochospongilla pennsylvania
Gemmosclere rotules almost equal in diameter, gemmosclere length less than the diameter of the smaller rotules; color gray, yellow or brown. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Trochospongilla horrida
12. Gemmoscleres with only one form represented; megascleres, if spined, with terminal spines sometimes directed toward tips (genus Radiospongilla) or not. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Gemmoscleres demonstrating two distinct or a graded series of forms; megasclere always spined and with terminal spines directed toward spicule tips. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Racekiela ryderi
13. Gemmosclere length ranging from 75 to 95 um, rotules with curved hooks; megascleres always with spines; foramen of gemmule situated in a recessed area and encircled by radially arranged gemmoscleres. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Radiospongilla crateriformis
Gemmosclere length much less than 75 um, rotules without curved hooks; megascleres smooth, weakly spined, or densly and coarsely spined, with all three conditions potentially present, gemmule not as above. . . . . . . . . . . .14
14. Gemmosclere length less than or equal to rotule diameter; rotules deeply incised to form no more than 12 long rays. . . . . . . . . . . . . Ephydatia muelleri
Gemmosclere length greater than rotule diameter; rotules weakly incised to form more than 13 long rays. . . . . . . . . . . . . . . . . . . . . . Ephydatia fulviatilis
Key to Genus & Species