G8 AMERICAN CORBICULAD^E. 



7. Pisidilim atoditum, HALDEMAX. Shell rounded-oval, elon 

 gated, very inequilateral, moderately convex, 

 Fig. 72. margins well rounded, beaks placed nearer the 



posterior side, small, slightly raised ; surface 

 smooth, striae not distinct, epidermis variable, 

 generally light straw color ; hinge-margin very 

 nearly straight ; cardinal teeth small, separate, 

 the anterior tooth larger and more prominent ; 

 lateral teeth small, not much elongated. 



Long. O.i5 ; Lat. 0.14; Diam. 0.09 inches. 

 P. dbditum. 



Hub. North America, in New England, in the 



States of New York, New Jersey, Pennsylvania, Ohio, Michigan, South 

 Carolina and California, in the Lake Superior region, at Montreal iu 

 Canada, and in Honduras. (Cabinets of Jay, Cuming, Prime, Smith 

 sonian Institution, and others.) 



Plsidiiim abditum, HALDEMAN, Proc. Acad. Nat. Sci. Phila. 1, 1841, 53. 



Cyclas minor, C. B. ADAMS, Bost. Proc. I, 1841, 48. 



Pisidium tenellum, GOULD, Agassiz, Lake Super. 1848, 245. 



Pisidium obscurum, PRIME, Bost. Proc. IV, 1851, 161. 



Pisidium rubellum, PRIME, loc. sub. cit. IV, 1851, 163. 



Pisidium minus, STIMPSON, Moll. New Engl. 1851, 16. 



Pisidium kurtzi, PRIME, Bost. Proc. IV, 1851, 162. 



Pisidium zonatum, PRIME, loc. sub. cit. IV, 1851, 162. 



Pisidium regulars, PRIME, Bost. Jour. VI, 1852, 363, pi. xii, f. 11, 12. 



Pisidium notatum, PRIME, loc. sub. cit. VI, 1852, 365, pi. xii, f. 20-22. 



Pisidium arcuatum, PRIME, loc. sub. cit. VI, 1852, 364, pi. xii, f. 14-16. 



Pisum abditum, DESHAYES, Brit. Mus. Cat. 1854, 282. 



Pisum minus, DESHAYES, loc. sub. cit. 1854, 281. 



Pisidium resartum, ING ALLS, in litt. 1855. 



Pisidium rubrum, LEWIS, in litt. 1855. 



Pisidium plenum, LEWIS, in litt. 1855. 



Musculium abditum, ADAMS, Rec. Gen. II, 1858, 451. 



Musculium minus, ADAMS, loc. sub. cit. II, 1858, 451. 



Musculium rubellum, ADAMS, loc. sub. cit. II, 1858, 452. 



Musculium obscurum, ADAMS, loc. sub. cit. II, 1858, 452. 



Musculium kurtzi, ADAMS, loc. sub. cit. II, 1858, 451. 



Musculium zonatum, ADAMS, loc. sub. cit. II, 1858, 452. 



Pisum obscurum, ADAMS, loc. sub. cit. II, 1858, 660. 



Pisum kurtzi, ADAMS, loc. sub. cit. II, 1858, 660. 



Pisum rubellum, ADAMS, loc. sub. cit. II, 1858, 660. 



Pisum zonatum, ADAMS, loc. sub. cit. II, 1858, 660. 



Pisidium retusum, PRIME, Proc. Zool. XXVIII, 1860, 322. 



Tliis species is distributed over such a vast area of country, and 

 varies so much according to the different localities in which it is 

 found, that it is hardly surprising that its numerous varieties 



