70 NEW- YORK FAUNA — MOLLUSCA. 



LlMNEA MEGASOMA. 

 PLATE IV. PIG. 70. 



(STATE COLLECTION.) 



L. nugaiomu. Sat, Long's Exped. St. Peters, Vol. 2, p. 263, pi. 15, fig. 10. 

 L, id. Adams, American Journal of Science, Vol. 40, p. 267. 



L. id. Haldeman, Monogr. Limniades, p. 13, pi. 3, fig. 1-3. 



Description. Shell very large, oval, inflated and rather solid. Whorls five, convex : body- 

 whorl with very obvious vertical grooves, which are crossed by very fine and often obsolete 

 lines. Spire short, rapidly diminishing, acute, often eroded. Suture deeply impressed. 

 Aperture oblong-ovate, capacious. Fold on the columella well marked. 



Color. Reddish or chesnut brown : epidermis rufous ; within brownish or whitish. Animal 

 blackish. 



Length, 1*0- 1"'5. 



This species agrees very well with the description assigned to it by Mr. Haldeman, with 

 the exception of the surface of the shell, which, in my specimens, was marked by broad fur- 

 rows or grooves more like his figure of L. jugularis ; from which, however, it is sufficiently 

 distinguished by its less elevated spire. It occurs near the shores of Lake Champlain. Not 

 a common species. 



LlMNEA GRACILIS. 

 PLATE IV. FIG. 73. 



(STATE COLLECTION.) 



Limnea gracilis. Say's Catalogue, pi. 1, fig. 10, 11. 



L. id. Adams, American Journal of Science, Vol. 40, p. 267. 



L. id. Haldeman, Monog. Limniades, p. 50, pi. 13, fig. 21. 



Description. Shell fragile, very slender. Whorls four to six, flat, and very obliquely re 

 volving. Suture distinct, deeply impressed. Body-whorl with minute incremental striae. 

 Pillar-lip unattached, without fold. Aperture oblong-oval, and rounded at both ends. 



Color. Whitish and pearl grey. Animal unknown. 



Length, 0*5- 1*0. 



This remarkable shell was discovered by Dr. Emmons in Lake Champlain, as yet its only 

 ascertained locality. It is with hesitation that I refer it to this genus, from the absence of 

 the oblique fold on the columella. The name of Acella as a subgenus has been proposed; 

 but if my views are right, it must form a distinct genus intermediate between Limnea and 

 Physa, or perhaps better at the end of the family. 



