24 NEAV UNIONIDiE OF THE 



green, obsoletely radiate, dark behind, with distant marks of growth ; umbonial slope 

 raised and obtusely angular ; posterior slope rather wide, somewhat flat and furnished 

 with small rays from the beaks to the margin ; cardinal teeth small, acuminate, 

 crenulate and double in both valves : lateral teeth long, lamellar and straight ; 

 anterior cicatrices distinct, rather large and well impressed ; posterior cicatrices con- 

 fluent and very slightly impressed ; dorsal cicatrices placed on the plate in the cavity 

 of the beaks; cavity of the shell rather deep and Avide; cavity of the beak deep and 

 angular, nacre white and very iridescent. 



Remarlcs. — This belongs to the group of which cariosus, Say, may be considered the 

 type. It is, however, a smaller species and rather more transverse, and the undula- 

 tions of the beaks are much smaller. The posterior slope is quite dark while the 

 remaining portion of the epidermis is smooth, polished and olive yellow. 



Umo scitulus. pi. 55, fig. 167. 



Tests licvi, ellipticu, inflata, valde infequilaterali, postico obtuse biangulatil, antico rotunclatfi ; valvulis sub- 

 tenuibus, aiitice crassioribus ; natibus prominentibus, ad apices undulatis ; epidermide lutea, undique 

 virido radiata ; dentibus cardinalibus parviusculis, erectis, acuminatis, crenulatis, in utroque valvulo 

 duplicibus; lateralibus loiigis, lamellatis subrectisque; margarita alba et valde iridescente. 



Shell smooth, elliptical, inflated, very inequilateral, obtusely angular behind and 

 rounded before; valves rather thin, thicker before; beaks somewhat prominent, 

 undulate at the tips; epidermis yellow, with green rays all over; cardinal teeth 

 rather small, erect, pointed, crenulate and double in both valves ; lateral teeth long, 

 lamellar and nearly straight ; nacre white and very iridescent. 

 Troc. Acad. Nat. Sci. 1860, p. 93. 



Ilah. — Tuscuuibia, Alabama. L. B. Thornton, Esq. 



My cabinet and cabinet of Mr. Thornton. 

 Diam. -7, Length 1-1, Breadth 2-1 inches. 



Shell smooth, elliptical, inflated, very inequilateral, obtusely angular behind and 

 rounded before ; substance of the shell rather thin, thicker before ; beaks somewhat 

 prominent, with small undulations at the tips; ligament rather large and dark brown ; 

 epidermis 3'ellow, with numerous green rays over the whole disk and with rather 

 distant marks of growth ; umbonial slope raised and rounded ; posterior slope slightly 

 raised, with numerous small rays; cardinal teeth rather small, erect, pointed, crenu- 

 late and double in . both valves ; lateral teeth long, lamellar and nearly straight ; 

 anterior cicatrices distinct and well impressed ; posterior cicatrices confluent and 

 slightly impressed ; dorsal cicatrices placed in the centre of the cavity of the l)eaks 

 and on the under side of the plate; cavity of the shell rather deep and wide; 

 cavity of the beaks rather shallow and subangular; nacre white and very iridescent. 



Remarhs. — This is a pretty little species nearly allied to radians (nobis), but it is 

 more oljlique, more angular posteriorly and not so much inflated, nor are the rays so 



