Sterki: North American Sph.eriid.e. 439 



38. Sphaerium tenue walkeri Sterki. 



Sphariiun walkeri Sterki, NauHlus, XIV, 1901, p. 141 (parlim). 



A small lacustrine, or deep-water, form, with the beaks broader and 

 less elevated, as is generally the case in lake forms of SpliCBria. 



Habitat. — Dredged from Lake Michigan in water twenty-four meters 

 deep. The form occurs also in Lake Michigan on the Indiana coast. 



39. Sphaerium mormonicum Sowerby. 

 SphcBriutn mormonicum Sowerby, Con. Icon., fig. 44. 



Habitat. — Cited as from Great Salt Lake. I have seen no specimens. 



The following four fossil species from the Tertiaries of Nebraska, 

 described at various times by Meek & Hayden, have not been seen 

 by the writer, who includes them in this catalog, as cited by Prime in 

 his Monograph. The last two may be species of Miisciilium. 



40. Sphaerium recticardinale Meek & Hayden. 



SphcBriutn recticardinale Meek & Hayden, Proc. Acad. Nat. Sci. Philada., i860, p. 

 176. 



41. Sphaerium planum Meek & Hayden. 



Sphcerium planum ^lEEKSiHAYDEt^, Proc. Acad. Nal. Sci. Philada., I. c, p. 175. 



42. Cyclas formosa Meek & Hayden. 



Cyclas formosa Meek & Hayden, Proc. Acad. Nat. Sci. Philada., 1856, p. 115. 



43. Cyclas subelliptica Meek & Hayden. 



Cyclas subellipticaMEEKSzHAYVKTS!, Proc. Acad. Nat. Sci. Philada., iSs(>< T>- US- 



Genus Musculium Link. 

 Calyculina Clessin. 



1. MuscuHum elevatum (Haldeman). 



Cyclas elevata Haldeman, Proc. Acad. Nat. Sci. Philada., I, 1841, p. 53. 

 SphcBrium. elevatum Prime, Man. Corb., 1865, p. 44. 



Habitat. — Georgia to Texas, Missouri, Illinois. 



2. Musculium orbiculare Sterki. 



Musculium orbiculare Sterki, Nautilus, XXVI, 1913, p. 140. 



Habitat. — Indiana, Illinois (originals), Louisiana, Texas, Minnesota 

 (?). Cf. Roper, Nautilus, X, p. 29. 





