﻿330 oni.igLARiA 



tolcrabl}- wcll-dcvclopcd lunule : beak sculpture stronj;', con- 

 sisting of four or five heavy, parallel ridges, which fall low in 

 front but are curved upward hehind ; epidermis smooth, gen- 

 erally shining, painted with niunoruus delicate, wavy, darker, 

 broken rays ; pseudocardinals strong, direct, and ragged ; lat- 

 erals short, nearly straight ; anterior muscle scars small, the 

 sides of the pit smooth, the bottom ragged ; front part of the 

 shell very solid, suddenly becoming rather thin just behind 

 the knobs ; male and female shells essentially alike. 



Animal having the branchice small, rounded below, inner 

 the larger, free from the abdominal sac in ]:)art ; marsupium 

 consisting of a few distinctl\' marked ovisacs (4 to 7), occupy- 

 ing a position just behind the center of the outer gills, project- 

 ing below the rest of the branchi:e. their bases rounded ; man- 

 tle cut away at the thinner ]>ortion of the shell ; anal opening 

 smooth or having only minute crenulations. 



Tvpe. ObUqnaria rcflexa Rafinesque. 



OiM.iouAKiA KUFLEXA Ratinesque. 



Shell irregularly oval, inflated, solid, inequilateral, with rath- 

 er high, full beaks, which are turned forward over a small 

 lunule, their sculpture consisting of three or four coarse, 

 oblique ridges ; posterior ridge well developed ; surface sculp- 

 tured with a central radial row of four or five strong, longi- 

 tudinally compressed knobs, and besides these there are occa- 

 sional slight corrugations or wrinkles ; epidermis generally 

 smooth and subshining, yellowish-green, usually covered with 

 delicate, wavy, more or less broken rays, often uncolored. 

 Sometimes these rays consist of small dots and again of ar- 

 row-head markings ; posterior end of shell obliquely tnmcate 

 above ; left valve with two ragged, radial, stumpy pseudocardi- 

 nals and two slightly curved laterals; right valve with one 

 triangular pseudocardinal. often with a vestigial tooth on each 

 side of it, and one double lateral : muscle scars small, the an- 

 terior ones rough ; beak cavities shallow : nacre white, straw- 

 colored, salmon or reddish, much thicker in front. Male and 

 fenuile shells scarcely differing. 



