156 NEW UNIONIDiE, MELANID^, ETC., 



Family LYMNEANA. 

 Genus POMPHOLYX * 



Testa rotundo-gibbosa, subtus retrorsa, stiperne plauulata, non umbilioata ; spira depressa ; apertuva am- 

 plissima, subi'Otunda, effusa ; labro acuto ; labio incrassato, planulato ; operculum nullum. 



Shell gibbosely rounded, drawn back beneath, above flattened, not umbilicate ; 

 spire depressed ; aperture very large, nearly round, effuse ; outer lip acute, inner lip 

 thickened, flattened ; no operculum. 



Proc. Acad. Nat. Sei., 1856, p. 80. 

 RemarTcs. — Among a number of specimens of Melania seminalis, Hinds, sent to me 

 by Dr. Trask from Sacramento Kiver, were four specimens of the above described 

 genus, which at a hasty glance might have been easily passed unrecognized. A little 

 comparison, however, would easily show that the constriction of the mouth and the 

 depression of the spire forbid the connection, feven with the genus. On a more criti- 

 cal examination it would be observed that the form of the aperture, as well as the 

 spire, would more closely connect it with some of the Ampullarice, particularly A. 

 neritoides, D'Orb. It cannot be placed, however, with that genus, having no opercu- 

 lum. It probably belongs to the family of Lymneana, but without the advantage of 

 examining the structure of its organs it would be impossible to decide definitely as to 

 the true position of the genus. Three of the four specimens before me had the soft 

 parts remaining dried up in the shell. There was no operculum, and we might ex- 

 * pect this from the efi"use form of the aperture. The absence of an operculum would 

 suggest its belonging to the Planorhes, but the absence of an umbilicus and its not 

 being convolute, forbid that connection. The general form reminds one of the genus 

 Vitrina. 



POMPHOLYX EFFUSA. PL 23, fig. 69. 



Testa parva, striata, rotundo-gibbosa, subtenui, effusa, luteo-cornea; anfractibus trinis, superne planulatis, 

 inferne convexis ; apertura subrotunda, dilatata, intus albida, maculata. 



Shell small, striate, irregularly rounded, rather thin, efiuse, yellowish horn-color ; 

 whorls three, flattened above, convex below; aperture rounded, dilate, within whitish 

 and spotted. 



Proc. Acad. Nat. Sci., 1856, p. 80. 



Hub. — Sacramento Eiver, California, Dr. Trask. 



My cabinet and cabinet of Dr. Trask. 

 Diam. -32, Length -25 inch. 



*nc/*<foxu|, bulla. 



