1. CORBICULACEA OF NORTH AMERICA G. L. Mackie, Department of Zoology, University of Guelph, Guelph, ON, N1G 2W1 CORBICULACEA Sphaeriidae Adult shell < 2.5 cm long Hinge teeth not serrated Adult shell > 2.5 cm long Hinge teeth serrated Hinge teeth absent Internal shell maculated with dark brown blotches. Only one species: Hinge teeth present Internal shell white, without maculations. Eupera cubensis Umbone central to subcentral Adult shell 8-22 mm long Umbone distinctly subterminal Adult shell < 8 mm long Genus Pisidium Adult shell heavy Shell without cap Adult shell thin Shell calyculate (with cap) Genus SphaeriumGenus Musculium Go to Sphaerium keyGo to Musculium key Go to Pisidium key Corbiculidae Corbicula fluminea Shell distinctly longer than high; Dorsal posterior margin distinctly longer than cap diameter Shell about as high as long; Dorsal posterior margin shorter than or subequal to cap diameter Genus Musculium Length Height Cap diam. Length Height Posterior margin Cap diam. Posterior margin Cap vertical, not tilted anteriorly Shell somewhat triangular in outline Cap tilted anteriorly Shell somewhat square or rectangular in outline Musculium transversum Musculium lacustre Cap diameter > length of dorsal posterior margin Cap diameter < length of dorsal posterior margin Musculium securis Musculium partumeium Genus Sphaerium Shell thick with heavy striae; surface dullShell thin; surface silky to glossy Shell distinctly longer than high Shell length and height about equal Shell inflatedShell compressed Adult shell > 1 cmAdult shell < 9 mm Oval in outline N. Pacific states Rhomboidal outline Central to Eastern N.A. Sphaerium striatinum Sphaerium fabale Sphaerium patella Sphaerium rhomboideum Temporary ponds only; Shell oval, with rest marks Permanent waters only Shallow to deep water; Great Lakes watershed only; Introduced Deep, cold oligotrophic water; Great Lakes & North latitudes Sphaerium occidentale Sphaerium corneum Sphaerium nitidum Sphaerium simile P. amnicum P. compressum P. casertanum P. adamsi P. conventus P. dubium P. cruciatum P. fallax P. henslowanum P. idahoense P. insigne P. punctatum P. punctiferum P. rotundatum P. supinum P. ventricosum P. walkeri Genus Pisidium Umbo flattened or with ridge Umbo rounded, without ridge Umbo flattened Entire shell ridged; OR, CA only Ridge U-shaped Ridge chevron-like Shell height > length Shell height < length Striae fineStriae coarse Adult shell > 8 mm long Adult shell < 8 mm long Shell glossy; deep, cold lakes Shell silky to dull C3 U-shaped; Great lakes watershed C3 J-shaped; Eastern N.A. Shell very glossyShell silky to dull Shell greatly inflated & pea-like Shell may be inflated but not pea-like Umbo anterior Umbo subcentral Umbo central to subcentral Umbo anterior Umbo centralUmbo subcentral Hinge narrow; Shell with iron deposits Hinge plate thick, heavy; Shell lacks accretions Umbo low, shell longer than high Umbo high, shell length ≈ height Shell longer than high P. subtruncatum P. milium P. lilljeborgi P. ferrugineum P. equilaterale Shell length ≈ height Umbo low, posterior margin angled Umbo inflated, shell elongate, posterior margin slightly curved P. nitidum Shell compressed deep, cold lakes Umbo subcentral Shell inflated, S.E. U.S.A. only Umbo anterior Adult 6-8 mm Adult <6 mm P. variabile Adult shell < 2 mm Adult shell > 2 mm Posterior dorsal margin long Posterior dorsal margin short Striae evenly spaced Striae unevenly spaced Umbo with ridge P. ultramontanum