﻿UNITED STATES. 55 



epidermis black and shining, coarsely, closely and transversely striate, with distant 

 marks of growth, in the young obscurely rayed ; umbonial slope rounded ; posterior slope 

 raised into a wing with about ten curved ribs enlarging rapidly towards the margin ; 

 cardinal teeth large, massive, crenulate and double in both valves; lateral teeth long, 

 lamellar, very stout, slightly curved, single in the right and double in the left valve ; 

 anterior cicatrices very large and distinct ; posterior cicatrices large and confluent ; 

 dorsal cicatrices large and placed on the plate within the cavity of the beaks ; palleal 

 cicatrix deeply impressed and distant from the margin of the disk ; cavity of the shell 

 deep and rounded; cavity of the beaks deep and subangular; nacre silvery white and 

 iridescent. 



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

 Branchim very large, nearly semicircular, inner ones very much the larger, free nearly 

 the whole length of abdominal sack. Palpvf rather large, subelliptical, rather thin, 

 attached obliquely to the mantle and united more than half way down the posterior 

 edges. Mantle thin, with a very broad somewhat thick margin, brownish on the pos- 

 terior edges, expanded in the postero-dorsal margin. Branchial opening small, with- 

 very light brown, obtusely conical papillge on the inner edges. Anal opening with nu- 

 merous very minute papillae on the inner edges. Super-anal opening very long, edges 

 dark brown, united slightly at the lower part. The whole mass nearly white. The 

 six specimens sent in alcohol J by Bishop Elliott, were all without ova in the branchial 

 uterus. The form of these therefore is not yet ascertained. 



Eemarks. — There is perhaps no species of the great group of folded TJniones more 

 remarkable or attractive than this, which I have great pleasure in dedicating to my 

 friend the Right Reverend Stephen Elliott, of Georgia, who has done so much, and 

 with the true spirit of science, to develope this branch of the natural history of his 

 State, within the bounds of which exist a larger number and more various species than 

 have been found in any other of the United States. It will be observed in these me- 

 moirs that he has brought to light not only a vast number of new species, but that he 

 has carefully collected them, with their soft parts, so that I am enabled to give the 

 chief points of their anatomical structure. 



This species is nearly related to U. atrocostatus, (nobis,) but it is larger, more quad- 

 rate and has larger folds. In the young there is a marked distinction in the Elliottii, 

 having a very remarkable golden yellow nacre posteriorly, which differs from any 

 other species I have seen. This peculiar tint I have observed only in the young and 

 half grown specimens of this species. There is a golden tint in the full grown IT. 

 dromas (nobis,) and some of its allied species, but the tint of Elliottii is more inclining 



* See note on page 43, on branchial uterus. 

 f Called by Brard lips or tentacles. 



% The specimens described in this paper, (so far as relates to the soft parts in alcohol,) may be found to 

 vary somewhat from living specimens. 



