VIVIPARA. lY 



purpurea) denticles, the intermediate with from seven to twelve, 

 the inner lateral with from five (sivainsonii) to ten (georgiana), 

 and the outer lateral with from five (subpurpurea) to sixteen 

 (bengalensis). Right tentacle as broad as the snout, and but little 

 shorter than the left, with its extremity truncated and excavated, 

 forming a sheath for the reception of the connate male organ, 

 which projects a little beyond when unsheathed or unfolded. 

 Cervical lappets of each side very large, and foJded, trough- 

 shaped, forming with the mantle distinct tubular conduits, on 

 the right side for the ingress, and on t\^\^ left for the egress, of 

 the water for respiration. Branchial lamime very numerous, 

 narrow, almost linear, and crowded in a single row, but variable 

 in width at base, and diverging at their tips so as 

 to appear to be in three or more rows. (Stimpson.) ^^' 



Operculum with the nucleus simple. Shell thin, , 



turbinated, sometimes umbilicated ; spire produced, (' ' 

 whirls round, smooth or carinated, covered with an ~'*^ 



,. ., . . , ,, . . Operculum of 



ohvaceous epidermis ; peristome thin, continuous, y, r/eorgiana. 

 simple anteriorly. 



Vivipara iiitertexta, Say. — Shell subglobose, yellowish-green or 

 brownish, wrinkled, and with minnte, very numerous, obsolete revolving, 

 deciduous lines ; spire depressed conic, obtuse, truncated, eroded at tip ; 

 volutions nearly four ; suture 



rather deeply indented ; umbili- Fig. 26. 



cus closed by the lateral exten- 

 sion of the columella. 



Greatest breadth, from four- 

 fifths to one inch ; length, about 

 the same. Inhabits Louisiana. 



We collected many of the shells 

 in the marshes near New Orleans 

 and on the banks of the Caron- Paludina intertexta. 



delet canal. It is remarkable for 



its globular form and for the numerous obsolete lines which seem like 

 equidistant deciduous corrugations of the epidermis, having no effect 

 whatever in modifying the calcareous surface, upon which it exhibits no 

 trace. In good specimens two or three obsolete, pale bands are visible by 

 transmitted light. {Sai/.) 



