﻿MARGARITANA 51 I 



Alasmodon (Snlcataria) papyraceum RAFiiXKSOUK, Cont. 



Monog., 1 83 1, p. 5. 

 Alasmodon {Snlcataria) badium Rafjnesquh, Cont. Monog., 



1831, p. 5- 

 Alasmodon (Amblamodon ) hians Rafinesque, Cont. Monog., 



1831, p. 5- 



Genus MARGARITANA Schumacher, 1817. 



Baphuc Mruschrn, Mus. Gevers, 1787, p. 472. 



Unio Rftzius, part. Diss. Hist Nov. Test. Gen., 1788, p. 16. 



Unio Oken, Lehrbuch der Nat., 181 5, p. 236. 



Mari^aritana Schumacher, Essai Nouv. Syst., 1817, p. 137. 



Dainalis (Leach manuscript) Gray, Pr. Zool. Soc. Lond., 



T847, P- 19^'- 

 Baplua H. and A. Adams, Gen. Rec. Moll., II, 1858, p. 499. 



Shell elongated, usually arcuate, rounded in front, almost 

 lacking a posterior ridge ; beaks rather low, the sculpture con- 

 sisting of a few coarse, parallel ridges, which follow the growth 

 lines; epidermis concentrically striate, brownish or blackish; 

 hinge teeth generally imperfect or not fully developed; two 

 more or less perfect pseudocardinals in the left valve, and one 

 in the right, often reduced to mere tubercles ; behind these the 

 hinge plate is narrow and rounded for some distance ; laterals 

 short, usuallv imperfect or wholly wanting; cavity of the beaks 

 rather shallow ; muscle scars large, those of the anterior rough- 

 ened, posterior elliptical ; nacre generally more or less covered 

 inside the pallial line with small muscle scars. 



Animal with very long gills, inner wider in front, free for 

 the greater part of their length from the abdominal sac, the 

 tAvo pairs united to their posterior ends, which project back- 

 ward for some distance, unconnected with the mantle; palpi 

 " very large, falcate, united half way posteriorly ; branchial 

 opening having crowded, often arborescent, papill?e arranged 

 in folds ; anal opening smooth or crenulate ; superanal opening 



