﻿UNITED STATES AND NORTHERN MEXICO. 343 



large or distinct. The cardinal teeth are very much alike, but the lateral teeth of 

 scitulus are longer. It has also a close resemblance on the other side to concavus 

 (nobis), but it is smaller, has the beaks less medial, has larger rays and a less number, 

 the epidermis is more yellow and the cardinal teeth are less compressed. It also ap- 

 proaches in outline and the rays to Novi-Eboraci (nobis), but is not so oblique. The 

 females seem to be much smaller than the males, and have three or four large green 

 rays over the enlarged umbonial slope. I have not seen the soft parts of this species. 

 Three of the specimens bear the enlarged female character in the shell, six that of 

 the form of males. Some of the specimens have more numerous and rather smaller 

 rays, and some of the broad rays are disposed to divide into capillary forms. One of the 

 specimens has the double lateral tooth on the right or reversed side, which is a very 

 rare occurrence, but which I have seen in several other species and have mentioned 

 elsewhere. 



Unio Johannis. PL 55, fig. 168. 



Testa, obliquo-elliptica, subinflata, postice obtuse angulata, valde insequilaterali ; valvulis subcrassis, antice 

 crassioribus ; natibus subelevatis ; epidermide tenebroso-viridi, ad umbones micante, postice lutea ; 

 dentibus cardinalibus subcrassis, compressis, suberectis; lateralibus curtis, rectis, subcrassis corrugatis- 

 que ; margarita alba et valde iridescente. 



Shell obliquely elliptical, somewhat inflated, obtusely angular behind and very 

 inequilateral ; valves rather thick, thicker before ; beaks rather elevated ; epidermis 

 dark green, yellow behind, shining on the umbones ; cardinal teeth rather thick, 

 compressed and somewhat erect ; lateral teeth short, straight, rather thick and rough ; 

 nacre white and very iridescent. 



Proc. Acad. Nat. Sci. 1859, p. 171. 



Hob. — Connasauga Kiver, Bishop Elliott, and Etowah River, Georgia, Rev. G. 

 White ; Alabama River, Dr. Budd. 



My cabinet and cabinets of Bishop Elliott, Rev. Mr. White and Dr. Budd. 

 Diam. *5, Length - 7, Breadth 1 inch. 



Shell obliquely elliptical, somewhat inflated, obtusely angular behind, rounded 

 before and very inequilateral ; substance of the shell rather thick, much thicker 

 before ; beaks rather elevated ; ligament very short, rather thin, light brown ; epider- 

 mis dark green, yellow behind, shining on the umbones and striate below, with two 

 or three distant marks of growth ; umbonial slope slightly raised and rounded ; pos- 

 terior slope moderately wide, usually bright yellow with two well marked green rays 

 on each valve passing from the beaks to the posterior margin ; cardinal teeth rather 

 thick compressed, somewhat erect, single in the right and double in the left valve ; 

 lateral teeth short, straight, rather thick and rough ; anterior cicatrices distinct, 

 small and well impressed ; posterior cicatrices distinct, small and moderately im- 

 pressed ; dorsal cicatrices placed under the plate and behind the cardinal teeth ; cavity 



