ORTMANN: FAMILIES AND GENERA OF NAJADES. 299 
Genus STROPHITUS Rafinesque. (1820.) 
(Simpson, 1900), p. 616.) 
Shell subelliptical, subovate, or subrhomboidal, inflated, with indis- 
tinct posterior ridge. Disk smooth. Beak-sculpture concentric, con- 
sisting of a few rather heavy bars curving sharply up behind, forming 
an angle there. Hinge-teeth quite rudimentary, only mere vestiges 
of pseudocardinals present, which sometimes disappear altogether. 
Inner lamina of inner gills free, or more or less connected. Mantle- 
connection between anal and supra-anal rather short. Marsupium 
formed by outer gills, when charged having the edge distended and 
secondary water-tubes. But the ovisacs do not remain simple, 
and are subdivided into a number of compartments running cross-wise 
in the gill from face to face; each compartment containing the ova and 
glochidia is well defined; placentule solid, persistent until they are 
discharged. 
Type S. undulatus (Say). 
This genus offers in the marsupial structure the highest specialization 
known among the Anodontine. In the hinge and the inner lamina of 
the inner gill we also see indications of a high stage of development. 
The beak-sculpture and other characters of the shell assign it a place 
in the Alasmidonta-series. 
Strophitus edentulus (Say). 
I have examined a great many specimens from all over Pennsylvania, 
from the Ohio, as well as the Lake Erie, Delaware, Susquehanna, and 
Potomac drainages. I have also seen specimens from the Erie drainage 
in Huron Co., Ohio (O. E. Jennings coll.), from the Potomac drainage 
in Maryland (collected by myself), from Lawrence, Douglas Co., 
Kansas (R. L. Moodie), and of the form called shafferiana Lea, from 
the Cumberland River in Kentucky (B. Walker). 
Bradytictic. The breeding season begins in July (earliest date 
July 11), and ends in April and May. Discharging specimens have 
82 It is not clear what the original Anodonta undulata of Say is. Most authors 
(including Simpson) have taken the common Strophitus of the Atlantic drainage 
for it; but this is not different from the western edentulus Say. Conner thinks 
he has re-discovered the real undulatus in the tide waters of the Delaware river, but 
I can only see a local form of edentulus in it (I have not seen its soft parts). The 
form I have investigated is surely the edentulus of Say. 
