THE NAUTILUS. 31 



from L. S. Frierson, collected August 1, 1912, in Sabine River, 

 Logansport, De Soto Par., La. 



Others were sent by H. E. Wheeler from the Ouachita River, 

 Arkadelphia, Clark Co., Ark., collected at various dates. 

 Among them were two gravid females, collected May 19, 1911, 

 one with eggs, the other with unripe glochidia. 



The specimens from. Ouachita River are not typical frier- 

 soni, but resemble this species greatly; they are quite var- 

 iable in shape, but in the average more oblique. Whatever 

 they are, the anatomy of these two forms is identical. 



The structure of the soft parts is that of the genus Pleuro- 

 bema, with the outer gills only marsupial. The placentae are 

 lanceolate and compressed. Glochidia not fully mature, but 

 their shape could be made out ; they are semielliptical, higher 

 than long, approximate size, length 0.13, height 0.15 mm. 



The soft parts seem to have been whitish in all. 



This species belongs near to P. riddelU, as described by me 

 previously (1. s., p. 262). I first thought they were this species, 

 till Mr. Frierson called my attention to friersoni, and I think 

 he is right. Whether the specimens from Jackson, Miss., are 

 actually riddelli, remains to be seen. 



PLEUROBEMA FASSINANS (Lea) (See: Simpson, 1900, p. 762). 



A number of specimens from North Fork Holston River, 

 Saltville, Smyth Co., Va., collected by myself on September 

 17, 1912. 



Anal opening separated from the supraanal by a short 

 mantle-connection, its inner edge with fine papillae. Bran- 

 chial with larger papillae. Posterior margins of palpi con- 

 nected for about one-half of their length. Inner lamina of 

 inner gills free from abdominal sac, except at anterior end. 

 In the female (many were examined) only the outer gills are 

 marsupial, having much more crowded septa than the inner 

 gills. No gravid females were found. 



In all specimens, the soft parts were grayish-white to pale- 

 brown ; in one case, foot and adductor muscles have been 

 marked as orange-brown. None of the shells has been marked 

 as having had red gonads. 



