440 UNIONIDiE, THEIR SOFT PARTS 



Anal opening rather large, with numerous small, brownish papilla). Super-anal open- 

 ing rather large, united below. Color of the mass yellowish white. 

 Columbus, Mississippi, Dr. Spillman. 



Unio penittjs, Con. New Pr. Wat. Shells, pi. 5, fig. 1. 



Branchial uterus occupies the posterior portion of the branchia? and extends below 

 the margin, which present a triple crenulate border. Branchial small, thin, rounded 

 below, and oblique posteriorly, inner ones much the larger, at the posterior end 

 united to the mantle by a V-shaped muscle, united the whole length of the abdominal 

 sack. Palpi very small, very thin, united on the posterior edges only at the extreme 

 upper part. Mantle very thin, with a wide margin, colored on the edges, maculate 

 on the posterior exterior edges, furnished below the branchial opening with minute 

 papilla? and with a small white fleshy mass, on each side, of a subsigmoid form, 

 rounded at the bottom and pointed at the top, and furnished with some crenulations 

 in the middle, outside of which there is a small, expanded, nearly black flap. 

 Branchial opening small, with rather large, brown papilla?. Anal opening small, with 

 numerous small, brown papilla?. Super-anal opening rather large, brown, and corru- 

 gate on the inner edges. Anus corrugate on the rim. Color of the mass white, 



Columbus, Mississippi, Dr. Spillman. 



Remarlcs. — This is a well characterized species, as well in the soft parts as the hard 

 outer parts. I have never seen in any other species the subsigmoid fleshy process on 

 the edges below the branchial opening. Its position is analogous to the caruncle of 

 parvus and other allied species, but the form is entirely different, the parvus having 

 it subrotund. In the only female specimen of penitus which I have there are below 

 this fleshy process, on each margin, three other processes very like papilla?, but they 

 are white and truncate at the end. The possession of crenulated edges on the 

 super-anal opening is also remarkable. The brown maculations on the posterior 

 exterior margin remind one of those found usually on Margaritana, but they are not 

 quadrate, being pointed above. The rays on the epidermis are somewhat like those 

 oisecuris, but are not so chain-like, but like a series of angles filling into each other. 



Unio dehiscens, Say, = (oriens, Lea). Disseminator vol. 2, p 308, and Am. Conch, pi. 24. 



A single male specimen only received. Branchice very wide, light liver brown 

 color, inner ones slightly the larger, free nearly the whole length of the abdominal 

 sack. Palpi rather large, sub triangular, united only at the upper posterior portion 

 of the edges. Mantle rather thick, thickened and light brown on the margin and 

 blackish on the dorsal margin around the ligament. Branchial opening rather large, 

 thickened and light brown inside and outside the edges, with rather large papilla?. 

 Anal opening rather large, thickened and light brown outside the edges, without 



