ORTMANN: monograph of the naiades of PENNSYLVANIA. 67 



the latter should be classed rather with P. cicairicosua. One of my specimens from 

 St. Marys agrees rather well with U. cicatricoides, but it has upon the disk a slight 

 indication of a depression, since the tubercles are cut off rather suddenly behind, 

 making the posterior part of the shell appear contracted; but the broad furrow of 

 P. cyphyus is not by any means developed. 



In sculpture, P. cyphyus represents a further reduction of the tubercles of 

 P. cicatricosus. They are rather poorly developed, but still show in most cases the 

 character of short, transverse ridges. Sometimes these tubercles have almost 

 entirely disappeared. Where they are better developed, in rare cases even the 

 vertical dividing lines of the ridges, seen so frequently in P. cicatricosus, are indi- 

 cated. 



Young specimens of P. cyphyus somewhat resemble in shape Tnincilla rangiana 

 (Lea). But the latter species has a more greenish olive epidermis, with more or 

 less distinct rays. 



There is considerable variation in the comparative length of the shell of P. 

 cyphyus. A short appearance is given to the shell by a smaller development of 

 the posterior slope, and such shells are decidedly more abimdant among young 

 individuals. Old specimens are, as a rule, greatly elongated, and in these it often 

 happens that the radial furrow becomes effaced. If such specimens have at the 

 same time poorly developed tubercles, they resemble in shape old specimens of 

 Fusconaia subrotunda, but they generally differ in the color of the epidermis, lighter 

 hinge, and chiefly in the color of the soft parts (light orange). Of course, if females 

 are at hand, no mistake is possible. 



Localities in Pennsylvania, represented in the Carnegie Museum: 



Ohio River, Shippingport and Industry, Beaver Co.; Coraopolis, Allegheny Co. (S. N. Rhoads). 



Monongahela River, Westmoreland Co. (G. A. Ehrmann). 



Allegheny River, Aladdin, Godfrey, Kelly, and Templeton, Armstrong Co. 



Locality in Pennsylvania represented in the Philadelphia Academy of Natural 

 Sciences: 



Beaver River, Wampum, Lawrence Co. (S. N. Rhoads). 



Other localities represented in the Carnegie Museum: 



Ohio-drainage : 

 Ohio River, Toronto, Jefferson Co., Ohio; St. Marys, Pleasants Co., West Virginia; Portland, Meigs 



Co., Oliio; Portsmouth, Scioto Co., Oliio. 

 Tuscarawas River, Ohio (Holland collection). 

 Wabash River, New Harmony, Posey Co., Indiana (A. A. Hinkley), 



