﻿502 AI, \SAt IDOXTA 



Margaro)i lUn'w) collinus L,\\.\, Syn., 1852, p. 27,; 1870. p. 35 

 .Hasinidonta collina Simpson, Syn.. U)00, p. 669. 



1 have never seen the animal oi this si^ecies and cannot he 

 certain as to its systematic position. The form of tlie shell, 

 and the heak sculpture, are like those of forms of . llasuiidonta 

 The teeth, though nearl\- or (juite perfect, are more like those 

 of that genus than of any L'nios I know of. They are only T; 

 little better developed than those of A. heterodon. 



Group of Alasmldonta holstoma. 



Shell suhsolid, beak sculpture rather strong^, decidedly dou- 

 bly looped, surface brownish, slightly rayed ; pseudocardinals 

 delicate ; laterals nearly or quite wanting. Animal like that of 



./. call' col us. 



Ai.AS.MiDONTA IK )i,si'( >x I A (Lea). 



Shell usually long rhomboid, rarely elliptical, suhsolid, con- 

 vex, inequilateral; beaks full but not high, their sculpture 

 strong, doubly-looped ridges, the hinder loop narrow and an- 

 gular ; posterior ridge rounded or disposed to be double, end- 

 ing behind in a rounded point or feeble biangulation at the 

 1)ase ; surface with irregular growth lines ; epidermis dull 

 greenish-brown or yellow-brown, rarely with slight rays; left 

 valve with two low, compressed teeth in front of the beak ; 

 right valve with a single. comi)ressed anterior tooth ; laterals 

 nearlv or (piite olisolete ; nacre bluish-white. 



Length 50. height 29. diam. 19 mm. 



Tennessee River system : headwaters of the Coosa River. 



Ty])e locality, Holston River. 

 .^fargaritaiia liolstonia Lka, Tr. Am. I'hil. Soc. \'l, 1838, p. 



42. pi. xiii, fig. :^/\ Obs.. 11. 1838, p. 42, pi. xiii, tig. T,/. 

 Margarita (Margaritana) holstoma Lea, Syn., 1836, jx 46; 



1838, p. 28. 

 Margaron (Margaritaiia) liolstonia Lka. Svn., 1S52, p. 44; 



1870, p. 70. 

 Sfrof^hifits liolstonia Coxkap, Pr. .\c. X. Sci. Phila.. \ I, 1853, 



p. jGt,. 



