108 DESCRIPTION OF NEW 



Remarks. — This species strongly resembles P. Dorfeuilliana, here- 

 in described, being nearly of the same size, and possessing most of its 

 characters. It differs, however, in the large solid tooth on the left lip 

 being more angular, and in the two teeth on the right lip being some- 

 what differently placed. In the striae it differs much, these being lar- 

 ger, much better defined, and passing entirely over the whorls. In 

 the umbilicus it is wider, and shows more of the two whorls. This 

 shell forms the fourth of a group, the form of the apertures of which 

 is exceedingly alike, viz. P. fatigiata (Say), P. plicata (Say), and P. 

 Dorfeuilliana (nobis). 



Continuation of Mr Lea's Paper. Read, January 1 9th, 1838. 



Unio Brownianus. Plate XXIV. fig. 116. 



Testa trigona, inflatd, vald^ incequilaterali, alata ; valvulis crassis ; natibus prominentibus ; 

 epidermide striata ; dentibus cardinalibus subgrandibus ; lateralibus longis ; margarita 

 alba. 



Shell triangular, inflated, very inequilateral, winged ; valves thick; beaks promi- 

 nent; epidermis striated; cardinal teeth rather large; lateral teeth long; nacre 

 white. 



Hab. River Amazon, South America. Captain George Brown. 



My Cabinet. 

 Cabinet of Captain Brown. 

 Diam. 1, Length 1, Breadth 2 inches. 



Shell triangular, inflated, very inequilateral, winged on the poste- 

 rior part; substance of the shell thick; beaks prominent; ligament 

 rather long and thin ; epidermis dark brown, finely striate, and polish- 

 ed on the umbones ; umbones inflated ; umbonial slope carinate ; car- 

 dinal teeth rather large and striate; lateral teeth long and nearly 



