ORTMANN: monograph of the naiades of PENNSYLVANIA. 47 



General distribution: Type locality, Ohio River (Rafinesque) . 



Simpson (1900) gives as the range of this species: "Mississippi-drainage 

 general!}^; streams falling into the Gulf of Mexico from the Alabama system west 

 to central Texas." This indicates a very wide distribution. In the Mississippi 

 it goes into Wisconsin (Barnes, 1823; Lapham, 1860), and southern Minnesota 

 (Grant, 1886; Holzinger, 1888), but its northward extension is generall}^ rather 

 restricted. Call (1895, p. 55) reports it from western New York, which is im- 

 confirmed, and is very questionable, judging from its absence in the headwaters of 

 the Allegheny in Pennsylvania, and its entire absence from the whole lake-drainage 

 in Pennsylvania, Ohio (Sterki, 1907a), Indiana (Call, 1896a) and Illinois (Baker, 

 1906). As our records show, it occurs in the tributaries of the Ohio in West Vir- 

 ginia and Kentucky, and goes up the Tennessee to northern Alabama, but is 

 absent from the upper Tennessee region, except the Hiwassee River. Westward 

 it goes to Iowa, Kansas, and Oklahoma, and its occurrence in Arkansas, and in 

 the Gulf-drainage from Georgia to Texas is well established. 



This species seems to belong more to the south and the west, but it has as- 

 cended the Mississippi to a considerable distance, and the Ohio practicalh^ through- 

 out its whole drainage, except the smallest headwaters in the north and east. 



It does not seem to be very abundant in the larger streams. I never found it 

 in the Ohio proper below the Pennsylvania state-line, although it is in the Cin- 

 cinnati list of shells. 



QuADRULA METANEVRA (Rafiuesque) (1820). 



Quadrula metanevra (Rafinesque) Simpson, 1914, p. 834. 



Plate IV, figs. 4, 5, 6. 

 Records from Pennsylvania: 



Rhoads, 1899 (Ohio River, Coraopolis, Allegheny Co., and Beaver, Beaver Co.). 

 Ortmann, 19096, p. 198. 



Characters of the shell: Shell of medium size, heavy. Outline subtrapezoidal, 

 subrhomboidal, or subquadrate, sometimes subtriangular, short, not longer, or 

 very little longer, than high. Beaks moderately elevated. Beak-sculpture con- 

 sisting of two or three subconcentric bars, which are angular and nodulous upon the 

 posterior ridge; anterior part rather straight, and curved upward in front, thick, 

 but not sharply marked. The nodulous portion is repeated upon the posterior 

 ridge in the shape of tubercles, while the anterior part of the following bars becomes 

 indistinct, and is soon supplanted by the sculpture of the disk. Occasionally the 

 third and fourth bars show an indication of double-looped structure, and sometimes 



