LYMNJEIDJE OF NORTH AMERICA. 317 



Lymnaa desidiosa MORSE, Amer. Nat., Ill, p. 651, 1870 (part). BAKER, 

 Nautilus, XXII, p. 20, pi. Ill, figs. 1-2, 1908. 



SHELL: Of medium size, solid, ovate to elongated in form; peri- 

 ostracum pale horn colored, darker in some specimens ; surface dull, 

 lines of growth crowded, conspicuous, crossed by fine impressed spiral 

 lines ; the body whorl is frequently malleated ; whorls five to six, regu- 

 larly and rapidly increasing in size, well rounded, the body whorl quite 

 convex; spire acutely conic or elongated, as long as or a little longer 

 than the aperture ; sutures well impressed, rather deeply in some speci- 

 mens; nuclear whorls V/2 in number, brownish horn in color, and in 

 outline like those of palustris; aperture ovate or roundly ovate, rounded 

 below and slightly angled above; outer lip with an internal varix; 

 inner lip narrow, triangular, reflected over the umbilical region, leaving 

 a small chink; the callus on the parietal wall is heavy and sometimes 

 causes the aperture to be continuous; there is a columellar plait and 

 the axis is slightly twisted. 



Length. Breadth. Aperture length. Breadth. 



15.00 7.50 8.00 3.00 mill. Say's autotype 



14.25 7.50 7.75 3.50 " 



15.00 8.00 8.00 4.00 " Williamsville, N. Y. 



14.00 8.00 8.00 3.50 " " " 



17.00 8.00 7.50 4.00 " Seneca Lake, N. Y. 



15.50 7.50 6.50 3.50 " 



TYPES: Autotypes, Acad. Nat. Sci., Philadelphia, two specimens, 

 No. 58731. 



TYPE LOCALITY : Cayuga Lake, N. Y. 



ANIMAL: Not examined alive, but alcoholic specimens appear 

 externally like palustris. 



JAW : As in palustris. 



RADULA ( PI. VIII, fig. I. ) : Formula /__V + * + i + ff *+ i+ 5 2 -V 

 (34-1-34) ; the teeth are in all essential respects like those of palustris; 

 the marginals of desidiosa begin more abruptly than is the case with 

 palustris. 



GENITALIA : Not differing from those of palustris; one specimen 

 gave the following measurements : 



Penis- Prost. Penis Penis-sac 



Penis. sac. Vas. def. duct. ret. ret. Shell. Locality. 

 1.50 2.75 10.00 3.50 2.25 2.00 14.00 New York. 



RANGE : New York to Indiana. A species of the humid division 

 of the Transition and Upper Austral life zones, and of the Canadian 

 and the Upper Mississippian regions. The specimens examined have 

 all been from the Carolinian division of the Upper Austral of western 

 New York. The Indiana record is that of Say on page 211 of his 



