﻿UNITED STATES. 193 



rather thick, thicker before; beaks a little prominent; epidermis dark chestnut, 

 without rays and shining; cardinal teeth rather small, low, obtusely conical and 

 crenulate ; lateral teeth very long and curved ; nacre salmon colored and very 

 iridescent. 



Proc. Acad. Nat. Sci., 1857, p. 171. 



Hah. — Flint river, near Macon, Georgia. J. C. Plant. 



My cabinet and cabinet of Mr. Plant. 

 Diam. 1*1, Length 2-2, Breadth 3"7 inches. 



Shell smooth, regularly elliptical, very much compressed, inequilateral ; substance 

 of the shell rather thick, thicker before; beaks a little prominent; ligament long, 

 large and dark brown ; epidermis dark chestnut, shining, without rays, with distant 

 broad lines of growth ; umbonial slope very low and rounded ; posterior slope com- 

 pressed and somewhat raised; cardinal teeth rather small, obtusely conical, crenulate, 

 disposed to be double in the right as it is in the left valve ; lateral teeth very long, 

 curved and corrugate ; anterior cicatrices distinct and well impressed ; posterior 

 cicatrices large, confluent and not deeply impressed ; dorsal cicatrices placed nearly 

 in the centre of the cavity of the beaks ; palleal cicatrix large, well impressed and 

 distant from the margin ; cavity of the shell very shallow and very wide ; cavity of 

 the beaks very shallow and rounded ; nacre salmon color and very iridescent. 



Soft Parts. — Branchial uterus not charged, but ova were found in the ovarium. 

 Branchim large, rounded below, inner one much the larger, free nearly the whole 

 length of abdominal sack. Palpi very small, subtriangular, free nearly the whole 

 length of the posterior edges. Mantle thin, thicker along the edge. Branchial 

 opening rather large, with small brownish papillae. Anal opening small, with 

 numerous small brownish papillae on the inner edges. Super-anal opening very large, 

 slightly colored on the inner edges and united at the lower part. Color of the mass 

 whitish. 



Remarks. — Unfortunately only a single specimen was received. It is a very 

 interesting species, and I am happy to dedicate it to J. C. Plant, Esq., of Macon, to 

 whom I am indebted for many fine and new species in this family. It is of a very 

 regular ellipse of nearly four inches in the axis major and two and a quarter in the 

 axis minor. It is remarkably compressed. In general character and in outline it is 

 near to Stonensis (nobis), and inclines towards Ugamentinus Lam. It is not so much 

 compressed, nor so transverse as the former, but is more compressed than the latter. 

 This specimen is entirely without rays. Younger and more perfect ones may have 

 them. The beaks are much eroded and therefore the characters cannot be made 

 out. 



