﻿252 DESCRIPTIONS OF 



Hob. — Sikkim, India. H. Cuming and Prof. Hanley. 



Cabinets of Mr. Cuming and Prof. Hanley. 

 Diam. *6, Length "9, Breadth 1*3 inch. 



Shell smooth, obovate, inequilateral, rather inflated, obtusely biangular behind; 

 substance of the shell somewhat thick; beaks slightly prominent; ligament very 

 short, thin and yellowish ; epidermis yellowish brown, without rays and striate ; 

 umbonial slope rounded ; cardinal teeth small, short, crenulate and double in both 

 valves ; lateral teeth short, somewhat curved, and widely separated from the cardinal 

 teeth ; anterior cicatrices distinct, small ; posterior cicatrices confluent ; dorsal cica- 

 trices situated on the under side of the plate, posterior to the cardinal teeth ; cavity of 

 the shell rather deep and rounded ; cavity of the beaks somewhat deep and sub- 

 angular ; nacre white and iridescent. 



Remarks . — I have only seen the two specimens of this small species, which Mr. 

 Cuming and Prof. Hanley have kindly sent for my inspection from England. Neither 

 of them have perfect beaks, and, therefore, the character of the apex cannot be 

 ascertained. The outline is so nearly approaching to roundness that it might almost 

 be classed with the subrotund group. It is not so rotund as circulus, (nobis), by any 

 means, but is near to U. Brownii, (nobis). It cannot be confounded with that shell, 

 however, for that species is compressed and this is quite inflated. 



Unio Dysonii. PI. 39, fig. 132. 



Testa sulcata, elliptica, subinflata, insequilaterali, postice subbiangulari ; valvulis subcrassis, antice 

 crassioribus ; natibus prominulis, ad apices lsevibus ; epidermide straminea, eradiata ; dentibus 

 cardinalibus crassiusculis, erectis, erenulatis, in utroque valvule- duplicibus ; lateralibus longis 

 subcurvisque ; margarita argentea et valde iridescente. 



Shell sulcate, elliptical, somewhat inflated, inequilateral, subbiangular behind; 

 valves rather thick, thicker before; beaks slightly prominent, smooth at the tip; 

 epidermis straw color, without rays ; cardinal teeth somewhat thick, erect, crenulate 

 and double in both valves ; lateral teeth long and somewhat curved ; nacre silver- 

 white and very iridescent. 



Unio Dysonii, Lea. Proc. Acad. Nat. Sci. 1859, p. 152. 



Hab. — Honduras. D. Dyson. 



Cabinet of Mr. Cuming. 



Diam. -6, Length 1*1, Breadth 1*8 inch. 



Shell sulcate, elliptical, somewhat inflated, inequilateral, subbiangular behind and 

 emarginate at postero-dorsal margin ; substance of the shell somewhat thick, thicker 

 before ; beaks slightly prominent, pointed at the tip and free from any undulations ; 

 ligament not long, rather stout and light brown ; epidermis straw yellow, without 

 rays, with very distant marks of growth ; umbonial slope slightly raised and rounded ; 

 posterior slope slightly raised, with two slightly impressed lines on each valve from the 



