﻿328 CYPROGENIA 



Unio stcgariiis Say, Am. Conch., \'I, 1834. — Conrad, Monoj^., 

 X, 1838, p. 83, pi. XLVi, fig'. I. — REiiVF., Conch. Icon., XVI, 

 1864. pi. XL, fig. 45. 



Utiio stcgan'us var. irroratiis IVktel, Conch. Sam., Ill, 1890, 

 ]). 168. 



Var. piisilla Simpson. 



A i)cculiar, dwarfed variety, ahout one-half the size of the 

 ordinary form and much inflated. 



Length 36, height 35, diam. 27 mm. 



Length 43, height 37, diam. 29 mm. 

 Cy progenia irrorata var. pusilla Simi'Son, Syn., 1900, p. 610. 



Typ€ locality, Green River, Kentucky. 



The species is quite variable in form, but it always is flat- 

 tened on the beaks and upper part of the disk and has the 

 characteristic color pattern, which I have described. It is 

 more inflated and generally more pustulous than the nearly 

 allied C. aberti, but there are intermediate forms that can only 

 be placed with difficulty. 



Cypkogenia aberti (Conrad). 



Shell somewhat rhomboid, solid, but slightly inflated, with 

 low, compressed beaks placed a little in front of the middle, 

 which are turned forward slightly over the lunule and have 

 very faint sculpture ; posterior ridge rather sharp above, grad- 

 ually becoming less distinct and sometimes slightly double in 

 the later growth ; disk flattened above ; posterior slope with a 

 wide, shallow, radial furrow behind the posterior ridge. Sur- 

 face with low, wide, concentric ridges, which are strongest 

 above the rest periods and in addition to this it is more or less 

 subvcrticallv wrinkled : epidermis scarcely shining, yellowi'^h- 

 green with dots and flecks of dark green arranged in broken 

 rays ; hinge plate enormously wide and flat ; left valve with 

 two low, radial pseudocardinals and two low, wide laterals, 

 the lower often blurred ; right valve with one pseudocardinal, 

 sometimes with a feeble one on each side of it. and a low 

 double or triple lateral ; beak cavities shallow, compressed ; 



