41 



THRACIA, Leach. 



Gen. Char. Valves unequal, more or less gaping- 

 posteriorly ; hinge without teeth, its ligament 

 attached to a sunken narrow fulcrum, its car- 

 tilage internal, bifid, seated between two lliick 

 equal processes or calli, one in each valve ; 

 sinus in the attachment of tlie in;intle short. 



A GENUS very properly separated by Dr. Leach from 

 Mija of Linnaeus and other authors. The equality of the 

 processes for the support of the hinge cartilage in tiie two 

 valves being a very strong character ; near the beak there 

 is a protuberance which may be considered as a rudimentary 

 tooth, and above this protuberance the old shell is usually 

 eroded. It has the strong epidermis of the Mi/aria and an 

 opaque not pearly substance. 



The recent species inhabit muddy or sandy shores in 

 temperate climates : a few only are known, and the fossil 

 ones are scarcely more numerous ; they occur in the ter- 

 tiary and newer formations. 



THRACIA pubescens. 



TAB. \ycxxx\.—jig. \. 



Spec. Char. Transversely elongated, ovate, con- 

 vex ; surface granular beneath the epidermis ; 

 posterior extremity truncated, the truncation 

 inclined towards the nearly straight ventral 



