FRESHWATER AND LAND SHELLS. 37 



Unio carbonarius. Plate XL fig. 32. 



Testa subtriangulatd, tumidd, transversa, incequilaterali, subemarginata ; valvulis crassis; 

 natibus subprominulis ; epidermide nigra ; dentibus cardinalibus grandiusculis ; lateralibus 

 parvis subcurvisque ; margarita purpurea ei iridescente. 



Shell subtriangular, swollen, transverse, inequilateral, subemarginate ; valves thick ; 

 beaks rather prominent; epidermis black; cardinal teeth rather large; lateral teeth 

 small and somewhat curved ; nacre purple and iridescent. 



Hab. River Medellin, Mexico. Dr Burrough. 



My Cabinet. 



Cabinet of Dr Burrough. 



Diam, 1-1, Length 1*4, Breadth 2-4 inches. 



Shell subtriangular, swollen, transverse, inequilateral, subemarginate 

 at the base ; substance of the shell thick, thinner behind ; beaks rather 

 prominent ; epidermis black, apparently without rays ; ligament rather 

 long; cardinal teeth rather large, double in the left valve; lateral teeth 

 rather short, and widely separated from the cardinal teeth ; anterior 

 cicatrices distinct ; posterior cicatrices distinct ; dorsal cicatrices placed 

 across the inferior part of the cardinal teeth; cavity of the shell rather 

 deep ; cavity of the beaks deep and angular ; nacre purple and irides- 

 cent behind. 



Remarks. — -The two individuals which I have before me were kind- 

 ly sent by Dr Burrough, now resident United States consul at Vera 

 Cruz. Ever prompt to promote the study of natural history, in the 

 various climes he visits, he has sent numerous objects from Vera Cruz, 

 with the view of increasing our cabinets and our knowledge. 



The carbonarius has a stronger affinity to U. crassidens (Lam.) than 

 any other species I am acquainted with. It is, however, a smaller shell, 

 with more proportional diameter, and a more intense purple than I have 

 seen in that species. The colour in the only two specimens I have 

 seen, is almost a chocolate, and may be said to resemble the nacre of 

 the gibbosus (Bar.). The black exterior and the dark interior, give 

 the shell a very sombre aspect — hence its name. 



VI. K 



