ORTMANN: FAMILIES AND GENERA OF NAJADES. 357 
Truncilla haysiana (Lea). 
Four males, one sterile, and one gravid female have been received 
from B. Walker, they are from the Cumberland River in Ken- 
tucky. 
Agrees in every particular with 7. triquetra, with exception of the 
inner edge of the mantle in front of the branchial in the female. Here 
the papilla of the branchial are not markedly distant from the outer 
edge, but in front of them the inner and outer edges of the mantle di- 
verge considerably, both describing a short curve in opposite directions, 
coming together again before they reach the middle of the ventral 
margin. They enclose a lanceolate or broadly ovate space of spongy 
structure and black-brown in color. The inner edge has four to six 
distinct papilla in its anterior part, which are brown. Back of them, 
toward the branchial, lies upon the edge a very remarkable, pure white 
caruncle, which, in the alcoholic material at hand, is rounded, without 
distinct shape or structure except a few crenulations. Inside of the 
inner edge runs a black streak. The color of the mantle around the 
branchial papilla and forward along the edge is dark black and brown, 
and thus the caruncle is sharply marked off by its color. Anteriorly 
the margin of the mantle is brown, and in the region of the anal and 
supra-anal it is spotted with brown. In the male the two edges of 
the mantle are very little distant from each other, the inner has small 
papilla, one of which is pure white, but is much smaller than the 
corresponding caruncle of the female. 
Marsupium more regularly kidney-shaped, than in 7. triquetra. 
Glochidia similar, but larger; length 0.24; height 0.23 mm. (see Plate 
Soe hie. 14). 
Truncilla penita (Conrad). 
This species, which, according to Walker (1910c, p. 77), belongs to 
the triquetra-group, has been described by Lea (Obs., X, 1863, p. 440). 
It has below the branchial ‘‘a small white fleshy mass . . . of a sub- 
sigmoid form, rounded at the bottom, and pointed at the top, and fur- 
nished with some crenulations in the middle.’’ There is no doubt 
that this mass is similar and homologous to the white caruncle de- 
scribed above in 7. haysiana. I have not seen anything like it in 
T. triquetra. But the presence of this organ, the function of which is 
unknown to me, serves to connect more closely the two groups to which 
T. triquetra and haysiana belong. 
