OETMANN: monograph of the naiades of PENNSYLVANIA. 247 



variety of locations, and Call (1900) says that it is found on sand, gravel, and 

 mud-bars, but preferably on the last. 



Genus Paraptera Ortmann (1911). 

 Ortmann, 1912, p. 330.1^^ 



Type Unio fragilis Rafinesque. 

 Only the type-species is positively known to belong to this genus, although 

 it is probable that several others go with it. The tjT^e has been found in our state. 



Paraptera fragilis (Rafinesque) (1820). 



Lampsilis gracilis (Barnes) Simpson, 1914, p. 181; Lampsilis fragilis (Rafin- 

 esque) Vanatta, 1915, p. 552; Lasmonos fragilis (Rafinesque) Utterback, . 

 1916, p. 152. 



Plate XV, figs. 4, 5. 6. 



Records from Pefinsylvania: 



Clapp, 1895 (Allegheny Co.) 



Marshall, 1895 (Allegheny River, Warren Co.)im 



Rhoads, 1S99 (Ohio River, Coraopolis, Allegheny Co., and Beaver, Beaver Co.) 



Ortmann, 1909&, pp. 192 and 202. 



Characters of the shell: Shell large, but thin. Outline subovate or subelliptical, 

 normally with a high posterior wing, which renders the outline subtriangular. 

 However, this wing may be obliterated, chiefly in old shells. There is also generally 

 a small anterior wing. Shell more or less symphynote at the wings. Anterior 

 margin rounded, imited with the upper margin in a sharp angle. Lower margin 

 more or less regularly curved. Upper margin straight, elevated posteriorly, 

 forming the posterior wing and angle. Posterior margin obliquely descending, 

 sometimes somewhat concave just below the upper posterior angle, joining the 

 lower margin in a broad curve, so that there is no posterior angle. Beaks low, 

 hardly elevated above the hinge-line, located in the anterior portion of the shell. 

 Beak-sculpture faintly developed, rudimentary, consisting of three or four fine bars, 

 the first of which is subconcentric, the others double-looped, but onlj' with the 



'='^ Utterback (1916, p. 151) uses for tliis genus, the name of Latinionos Rafinesque (1831). How- 

 ever, the type of Lasmonos (L. fragilis Rafinesque, 1831) is not Unio fragilis Rafinesque (1820), but 

 Unio leptodon Rafinesque (1820), for which Rafinesque proposed the subgenus Leptodea in 1820. Thus 

 Lasmonos is a synonym of Leptodea. If U. leptodon should prove to be congeneric with Paraptera fragilis, 

 then, of course, my Paraptera should give way, not to Lasmonos, but to Leptodea. 



'^ I doubt the correctness of this locality. In the Allegheny I found tliis species as far up as southern 

 Armstrong County, where it is very rare. No trace of it was seen above Oil City. 



