﻿UNITED STATES. 221 



papillse. Anal opening seems to have no papillae, but in living specimens they may 

 perhaps be observed. Super-anal opening rather long and colored on the edges. Color 

 of the mass whitish. The muscular attachments to the valves are unusually large 

 and strong. The fine specimen figured was taken in the Scioto River, near Chilicothe, 

 Ohio, by Mr. Henry Moores, to whom I am indebted for it. 



Unio parvus Barnes * PI. 29, fig 102 and 102 a. 



Soft parts. — Branchial uterus occupies the posterior half of the outer branchiae, very 

 like to heterodon (nobis), and consists of about a dozen branchial ovisacks on each side, 

 with well marked divisions and extending below the margin of the branchiae.! 

 Branchiae small, inner one somewhat the larger, rounded below, free more than half 

 the length of the abdominal sack. Palpi rather small, subtriangular, united halfway 

 down the posterior edges. Mantle rather thick, thickened along the border. Branchial 

 opening with numerous light brown papillse on the inner edges, the edges being black, 

 the opening terminating below on each side with a black spongy looking mass, 

 resembling the lachrymal caruncle of the human eye, except in color.J Anal opening 

 small, with numerous small papillae. Super-anal opening large, colored on the exterior 

 edges, united below. Color of the mass whitish. 



Embryonic shell very light brown, elongate pouch-shape, very nearly a regular 

 ellipse, truncate at dorsal margin. It is allied to Unio rectus Lam. in outline, but is 

 not so much truncate. 



RemarJcs. — Fig. 29, pi. 102, represents the form of the branchial uterus and the 

 caruncle like mass on each side of the mantle. In an alcoholic specimen received 

 from Dr. Spillman, of Columbus, Mississippi, in November, I found the uterus charged 

 with embryos sufficiently perfected to be extruded ; but in another from Mr. Shaffer, 

 of Cincinnati, in- a living state, in May, the parent extruded a number of white 

 branchial ovisacks, which remained attached to the margin of the shell as represented 

 in fig. 2 a. The ova from these sacks, on examination under the microscope, presented 

 a round form, with clear albuminous matter surrounding three vittelary round masses. 

 The form of the branchial ovisack was cylindrical, with the ends pointed and the 

 whole slightly curved, the whole length being nearly two-tenths of an inch long and 

 one-twentieth in diameter. On opening the specimen from Cincinnati in a living 

 condition, I found that the caruncle-like mass had the power of contraction and 

 dilation. In its normal condition this is nearly round and less than the twentieth of an 



*Am. Journ. Sci., 1823. 



t The females received in September from Mr. Moores of Chilicothe, Ohio, had no ova in the branchial uterus, 

 but the ovaries were filled. Those received from Mr. Shaffer, of Cincinnati, in May, had the branchial uterus 

 filled with embryos. 



X U.paulus (nobis) and glans (nobis) also have the same kind of round mass, which, however, in the former 

 species is red, while in the latter it is white. In a single specimen of paulus I found this mass to be reddish. 



