ANCYLUS. 



143 



Ancylus rividaris, Say (Oct. 1S19), J. A. N. S. I, 125 (1819) ; Nicli. 

 Enc. ed. 3: ed Bi.nn. p. 60.— IIaldeman, Mon. 4, pi. i, f. 1 (1844). 

 — DeKay, N. Y. Moll. 12, pi. V, f. 98 a, h (1843).— Mrs. Gkay, Fig. 

 Moll. An. cccx, f. 5. — IS'ut of Gould ( =^-1. parallelus). 



Also noticed in Virginia and Wisconsin. Tlie figure is copied 

 from Haldemau. 



Ancylus tardus, Say. — Shell conic depressed ; apex behind the 

 middle obtuse, rounded, inclining backward but not laterally ; line from 

 the apex to the posterior tip rectilinear ; line from the apex to the anterior 

 tip arcuated ; aperture oval, not distinctly narrowed at one 

 end. Length a little over three-twentieths (4.25), breadth 

 one-tenth of an inch. 



Differs from A. rivularis. Nob., which has the apex leaning 

 towards one side, and the aperture narrower at one end. It 

 is less elongate than Jluviatilis, Drap., which has an acute and 

 laterally inclined apex. 



It inhabits the Wabash River. (Say.) 



Ancylus tardus, Say, N. H. Diss. Jan. 15, 1840,; Descr. '26: ed. Binney, 

 149.— Haldeman, Mon. 7, pi. i, f. 3 (1844).— Adams, Shells of Vt. 

 164, fig. (1842).— DeKay, N. Y. Moll. 13 (1843). 



Mr. Say's type is in the collection of. the Philadelphia Academy. 

 The species is said to have been found also in Yermont and the 

 District of Columbia. The figure is copied from Haldeman. 



Ancylus calcarius, DeKay. — Shell conic, calcareous, opaque. 

 Apex not central, moderately prominent ; aperture oval, 

 entire ; the curves on the longest sides dissimilar. In very 

 minute specimens, the edges somewhat everted. Epidermis 

 rufous, extending beyond the edge of the aperture ; within, 

 bluish-white, darker towards the apex. Length 0.3, height 

 0.12. 



The specimen which furnished the above description was 

 one of the largest which I have seen. They are more commonly of the 



Fig. 240. 



Ancylris 

 calcarius. 



