﻿290 OnOVARTA 



tliat of the male and female being generally slightly dififere'iti- 

 ated. The female has a highly organized marsiipium much like 

 that of I.ompsiUs. Vnio ellipsis of Lea and its ally U. castaneus 

 differ much in shell characters from the typical Obovarias aiul 

 form a group that is certainly worthy of subgeneric rank. 



Kl•;^■ To Tiir: spixmics oi- ( )1!o\ai<ia. 



Shell nearly or quite equilateral. 



IJeaks very high and curved forward. O. rctusa. 



Short, inllatcfl. dull colored, decidcdh- lighter 



behind. O. circiilus. 



Sul)Com])ressed to subinflated, smoky, subshining. O. lens. 

 Rather bright, more or less rayed. O. unicolor. 



v^iuall, yellowish, or \\\\\\ a lirown tlusli. 0. leibii. 



Obovate, small. 0. mix. 



Nearl\- orl)icular, blackish. O. rotiilata. 



Shell decidedly inequilateral. 



IJeaks subterminal, umbonal region inflated. 



Rather large, not dark colored. O. ellipsis. 



Small, dark colored. O. castauea. 



Ueaks subcentral, umlional region subcompressed. 



O. jacksouiana. 

 Subgenus Op.ovaria s. s. 



Shell retrose to short oval ; beaks high, central ; ])seudocar- 

 dinals rarely parallel with the laterals ; cavity of the beaks 

 deep, subcompressed : nacre bluish-white or purple. Animal 

 wath the characters of the genus. 



Orovaria rrtusa (Lamarck). 



Shell irregularly quadrate, solid, inflated, with very high 

 beaks, which are turned most decidedly forward over a well- 

 defined lunule ; nearly straight or somewhat rounded at the 

 dorsal line, subtruncate behind, curved or nearly straight at 

 the base ; posterior ridge rather high and rounded ; surface 

 sculptured with low, wide and irregular concentric ridges: 

 e])idermis vellowish-brown, somewhat cloth-like in fresh speci- 



