﻿UNITED STATES. 223 



largest size of the shell of one taken by me near Cincinnati, is in breadth 8, in length 

 51 and in diameter 3£ inches. The two valves, without the soft parts, weighed 2 

 pounds, 9 h ounces These dimensions are greater than those of any specimens of 

 which I have any account. 



The figure is intended to represent the position of the branchial uterus as existing 

 in the four leaves of the branchiae. The two of the right side are prominent and give 

 a very correct idea of these masses. The right palpus lying on the abdominal mass is 

 also correctly displayed. The specimen having been some time in alcohol, did not 

 present the means of giving the papillce of the branchial opening in a natural state, 

 and this part will, therefore, be found to differ from the drawing, somewhat, in living 

 specimens. 



Unio ' stramineus Con* PL 30, fig. 106. 



Soft parts. — Branchial uterus occupies the posterior end of the outer branchiae. Ova 

 were found in the ovarium,- but none in the uterus, which, however, consisted, in the 

 only specimen before me, of thirteen small sacks on each side, protruding beyond the 

 edge of the branchiee ; these sacks are blackish on the lower ends;, which color is 

 caused by a black secretion within.' Branchiee rather large, slightly curved below, 

 inner ones the larger, united the whole length of abdominal sack. Palpi rather large, 

 subelliptical, united halfway down the posterior edges. Mantle very thin, very white, 

 with a rather broad, somewhat thickened border. The inferior posterior edges, for a 

 short distance below the branchial opening, have very small whitish papillae, over 

 which numerous small black spots are dispersed, the base of the papillae being defined 

 by a black line, at the upper end of which there is a small round black spot, like an 

 eye. Along the basal line the papillae are continued to the middle, growing smaller 

 as they approach this their terminal point. These papillae are remarkable, being 

 thickly set, perfectly white and look like rows of fishes' teeth. Branchial opening 

 rather large, with numerous whitish, elongate papillae, enlarged at the base and 

 pointed at the termination. Anal opening very small, with numerous, thickly 

 set, whitish papillae on the inner edges, which are more remote than usual 

 from the outer edges. Anus small, crenulate on the edges and pointed. Super-anal 

 opening rather small, colored within and united below. Color of the mass unusually 

 white. 



Remarks. — I have had but a single specimen to examine, but it is in remarka- 

 bly fine condition, having a clean and perfect epidermis, with the posterior slope 

 covered by well defined capillary rays, and with rays on the beaks diverging from 

 the tips. It was sent to me by the kindness of Dr. Spillman, of Columbus, Mississippi. 



* Am. Jour. Sci., Vol. 25, pi. 1, fig. 6. 

 57 



