PLATE CXL. 



MACTRA HIANS. 



GAPINGy OR OBLONG MACTRA. 

 GENERIC CHARACTER. 



Animal a Tethys. Shell bivalve : valves equal ; sides unequal * 

 middle tooth of the hinge complicated, with a small hollow : lateral 

 teeth remote and inserted into each other* 



SPECIFIC CHARACTER. 



Shell oblong, rather arcuated, coarse, gaping anteriorly^ and the 

 hinge placed very far back. 



Mactra hians : testa oblonga sub-arcuata rudi antice hiante, cap* 



dine sufrterminali. 

 Mactra hians. Soland. Mas. Port, 



Da Costa and some other Conchologists have very erroneously 

 been led to conclude, that this, and Mactra lufraria, are the same 

 species, although they differ in almost every particular. The pre- 

 sent shell is much wider in proportion to the length than M. lutraria ; 

 and of a more incurvated shape : it is also a thicker and coarser 

 shell , and has the hinge placed much further back than in the other 

 species. Dr. Solander, who described it in the catalogue of the 

 Portland Museum, gave it the specific name of hians, from its re- 



H 2 



