ORTMANN: FAMILIES AND GENERA OF NAJADES. 325 
green rays. Male and female shells differing in shape, but the dif- 
ference often hardly noticeable. 
Soft parts agreeing with those of Obovaria in every respect; the 
glochidia also of the same type. 
Type JN. plicatula Charpentier. 
In its anatomical structure this genus is indistinguishable from 
Obovaria. The differences are all in the shell. But while Obovaria 
is primitive in its shell, Nephronajas inclines toward the genera of the 
Lampsilis-type, in fact its species have been considered, at least 
temporarily, to belong to Lampsilis. The subgenus Pseudoén of 
Obovaria connects this genus with Obovaria, and so we have an almost 
complete series. 
The nomenclature of this genus is doubtful. Of the species, which 
belong here, two (/igamentina and perdix) stand according to Simpson's 
system in Lampsilis, and a third (sapotalensis) in Nephronajas. 
Since Lampsilis is retained for other forms, only Nephronajas is 
available. But the anatomy of the type species of Nephronajas 
(plicatula) remains as yet unknown, and it is possible that it may 
differ in anatomy from sapotalensis. In the latter case, of course, 
Nephronajas could not be used for the present genus, and a new name 
would have to be chosen. 
Nephronajas ligamentina (Lamarck). 
Numerous specimens from the Ohio drainage in western Penn- 
sylvania have been investigated. In addition specimens have been 
seen from the Ohio River in West Virginia and Ohio (collected by 
myself), from the Cumberland River in Kentucky (var. gibba), 
received from B. Walker, and from the Ouachita in Arkansas, received 
from H. E. Wheeler. 
Typically bradytictic. The breeding season begins in August, and 
specimens with eggs are present in this month and the beginning of 
September. Later on only glochidia are observed. Specimens with 
glochidia have again been observed in May, and the discharge must 
take place in this month, for in June and July no gravid females 
have ever been found, although numerous specimens have been in- 
vestigated. 
.The soft parts have been discussed by Lea (Obs., X, 1863, p. 424) 
and Simpson (in Baker, 1898, p. 108). 
Anatomy in every particular like that of Obovaria. The inner edge 
