248 ANNALS OF THE CARNEGIE MUSEUM. 
This form is very likely the southern representative of the foregoing. 
It agrees with itin every respect. In one of the specimens from Louisi- 
ana and three from Arkansas the supra-anal was separated from the 
anal, in the others this separation was absent. The inner edge of 
the anal is finely crenulated. The posterior margins of the palpi are 
connected for about one-third of their length, and the inner lamina of 
the inner gills is free {rom the abdominal sac. 
The gill-structure of the females is identical with that of C. undulata. 
The gravid female had only a few glochidia in the outer gills, while the 
inner ones were yet partly charged, and both suprabranchial canals, 
as well as the cloacal chamber, were filled with masses of loose glo- 
chidia, partly sticking together, but not in the shape of placente. 
Glochidia like those of C. undulata. Length c.20; height 0.21 mm. 
Crenodonta heros (Say). 
According to the description and figure given by Lea (as multi- 
plicatus, Obs., VII, 1860, p. 222, pl. 30, fig. 105), this species without 
doubt belongs here. 
Crenodonta trapezoides (Lea). 
I have received, from L. S. Frierson, one male and two females from 
Bayou Pierre, De Soto Parish, Louisiana (collected Aug. 6, 1910), 
Fic. 5. Crenodonta trapezoides (Lea). Male, from Bayou Pierre, De Soto 
Parish, La. (Carn. Mus., No. 61, 4,586.) 
from A. A. Hinkley two females from Pearl River, Jackson, Hinds Co., 
Mississippi (collected Nov. 5, 1910), and from H. E. Wheeler a male 
