68 AMERICAN CORBICULAD^. 



7. Pisidium abdituni, Haldemax. — Shell rounded-oval, elon- 

 gated, very inequilateral, moderately convex, 

 ^^S* '"• 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. 0.15; Lat. 0.14; Diam. 0.09 inches, 

 P. abditutn. 



Hah. 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.) 



Pisidium ahditum, Haldeman, Proc. Acad. Nat. Sci. Phila. 1, 1841, 53. 



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



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



Pisidium obscurtan, Prime, Bost. Proc. IV, 1851, 161. 



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



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



Pisidium Icurtzi, Prime, Bost. Proc. IV, 1851, 162. 



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



Pisidium regulare, 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, 



Pisnm ahditum, Deshayes, Brit. Mus. Cat. 1854, 282, 



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



Pisidium resartum, Ixgalls, in litt. 1855. 



Pisidium rubrum, Lewis, in litt. 1855. 



Pisidium plenum, Lewis, in litt. 1855. 



Musculium ahditum, Apams, 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. 



This species is distributed over such a vast area of country, ainl 

 varies so much according to the different localities iu wliicli it is 

 found, that it is hardly surprising that its numerous varieties 



