﻿NliPHRONAiAS 261 



Rather compressed and decidedly biangulate behind. The 

 shell is nearly smooth, and sometimes has a slightly silky ap- 

 pearance when fresh. 



Nephronatas orkgonensis (Lea). 



Shell irreg'nlarly obovate or elliptical, subinflated, subsolid, 

 with a moderate posterior ridge ; beaks not high or full, their 

 sculpture not observed ; surface slightly sulcate, dull yellow- 

 ish-green with a few faint, rather narrow rays ; left valve with 

 two subcompressed, ragged pseudocardinals and two strong 

 laterals ; right valve with two pseudocardinals, the upper small- 

 er, the two separated by a parallel sided socket and one lateral ; 

 muscle scars well impressed ; nacre bluish-white, scarcely 

 shining. The male shell is slightly rounded on the base ; that 

 of the female has a decided marsupial swelling. Both shells 

 are feebly biangulate behind, the biangulation in the female 

 being considerably elevated above the base. 

 Length 55, height 32, diam. 20 mm. 

 NicaragLia ; Guatemala. 

 Unio oregonensis h^A, Pr. Am. Phil. Soc, V, 1852, p. 252; Tr. 

 Am. Phil. Soc, X, 1852, p. 275, pi. xxii, lig. ^^ ; Obs., V, 

 1852, p. 31, pi. XXII, fig. 33. — MusGRAVE, Phot. Conch., 1863, 

 pi. II, fig. 5. — SowERBY, Conch. Icon., XVI, 1868, pi. lxxiv, 



%• 383- 

 Margaron (Unio) oregonensis Lea, Syn., 1852, p. 29; 1870, 



P- 45- 

 Nephronoias oregonensis Simpson, Syn., 1900, p. 594. 



Unio radiatnliis von Martens, Biol. Cent. Am., Moll., 1900, 



p. 518, pi. XXXIX, figs. 8, a, b. 



Very clo'sely related to A', goascoranensis, macnielii, and 

 roivellii, and certain specimens can hardly be assigned to their 

 species. All the specimens I have seen of this species are 

 somewhat rayed, they are not quite so smooth nor so wide 

 behind as macnielii nor so inflated as fully adult roivellii. 



A careful comparison of von Martens' figures and descrip- 

 tion of his Unio radiatulus convinces me that it is the same 

 as Lea's oregonensis. There is a considerable number of spec- 



