OHTMANN: monograph of the naiades of PENNSYLVANIA. 257 



drainage in New York, Waterford, Saratoga Co. (De Kay, 1843) Troy, Rensselaer 

 Co. (Aldrich, 1869). Compare also Marshall (1895). 



Westward it extends to eastern Kansas (Scammon, 1906), and is also present 

 in the southern tributaries of the Ohio in West Virginia, Kentucky, Tennessee 

 (Marshall, 1895; Lewis, 1871; Wilson & Clark, 1914; Carnegie Museum) and 

 northern Alabama (Call, 1885; Carnegie Museum). In the Clinch River it 

 reaches Virginia. 



Within the range thus indicated, this species seems to be present chiefly in 

 the larger rivers, but sometimes it is found in rather small streams."' Judging 

 from the Ohio below Pennsylvania, it is a species of the shell-banks in the deep 

 chaniiels, and is taken in great numbers by the clam-diggers, but rejected as useless. 

 According to Baker (1898a) Call (1900) and Scammon (1906) it lives in the larger 

 lakes and rivers on muddy bottoms, but it certainly is not often fomid in mud in 

 Pennsylvania, where it occurs mostly in gravel. 



Toward the south P. alata just reaches Kansas and (in the Tennessee) northern 

 Alabama. Beyond these stations, it is represented by allied, but distinct species 

 or forms. The true P. alata is positively missing from the Alabama-drainage. 

 Simpson (1914, p. 164) reports a form from this region, which is also represented 

 in the Carnegie Museum from the Coosa River, called var. poulsoni (Conrad). 

 This indeed closely resembles P. alata, but in my opinion is a variety of P. purpurea 

 (Lamarck). I cannot go into details here, but we have in this case probably to 

 deal with an interesting instance of " convergency. 



}j 



Genus Toxolasma Rafinesque (1831). 

 Carunculina Ortmann, 1912, p. 337 (subgenus of Eurynia) ; Carunculina Simpson, 

 1914, p. 148 (subgenus of Lampsilis); Toxolasma, Frierson, 1914, p. 7; 

 Carunculina (genus) Ortmann, 1914, p. 68. 



Type Unio lividus Rafinesque."^ 

 Only one species is known from Pennsylvania. 



'"Its absence in the Tuscarawas River in Ohio has been noticed by Sterki (1907). Tliis corre- 

 sponds to its absence in the Beaver River in Pennsylvania. 



1'^ This is the Tennessee-Cumberland form of U. glans Lea. Particulars have been published else- 

 where. 



