Ortmann: Families and Genera of Najades. 299 



Genus Strophitus Rafinesquc. (1820.) 

 (Simpson, 19006, 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; placentuke solid, persistent until they are 

 discharged. 



Type .V. undulatus (Say). 32 



This genus offers in the marsupial structure the highest specialization 

 known among the Anodontince. 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 Alasniidonta-sevies. 



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 



32 It is not clear what the original Anodonla 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. 



