24 DESCRIPTION OF NEW 



Unio tampicoensis. Plate VII. fig. 18. 



Testa ovata, injiata, transversa, subcarinata, inmqv.ilaterali ; valvulis crassis ; natibus 

 subprominulis ; epidermide nigricanle ; dentibus cardinalibus magnis ; lateralibus longis, sub- 

 rectis magnisque ; margarita alba et iridescente, rarb rosed. 



Shell ovate, inflated, transverse, subcarinate, inequilateral ; valves thick ; beaks 

 somewhat prominent ; epidermis blackish ; cardinal teeth large ; lateral teeth long, 

 rather straight and large; nacre white and iridescent, rarely rose coloured. 



Hab. River Tampico, Mexico. 



River Medellin, Mexico. Dr Burroiigh. 



My Cabinet. 



Cabinet of Dr Burrough. 



Cabinet of Academy of Natural Sciences. 



Diam. 1-7, Length 2-8, Breadth 4-3 inches. 



Shell ovate, inflated, transverse, subcarinate, inequilateral ; substance 

 of the shell thick, thinner behind; beaks somewhat prominent; liga- 

 ment large and long; epidermis nearly black, and apparently without 

 rays ; cardinal teeth large, and deeply cleft in the left valve ; lateral 

 teeth long, rather straight, and large ; anterior cicatrices distinct ; pos- 

 terior cicatrices confluent ; dorsal cicatrices placed across the cavity of 

 the beak, and on the inferior part of the cardinal teeth ; cavity of the 

 shell large; cavity of the beaks somewhat deep and angular; nacre 

 white and iridescent, rarely rose colour. 



Bemarks. — The specimen figured here, I owe to the kindness of 

 Richard Ronaldson, Esq., who procured it from the commander of a 

 vessel trading to Tampico. It was brought from some distance above 

 that city. Dr Burrough subsequently procured the same species from 

 the river Medellin, ten miles south of Vera Cruz. It is a fine shell, 

 and has not much resemblance to any one of ours. It perhaps, in out- 

 line and in form of the teeth, most resembles U. crassus (Say). In the 

 older specimen, the epidermis is almost black — in the younger, it is of 



