ORTMANN: monograph of the naiades of PENNSYLVANIA. 161 



In addition, I have collected two specimens in the Delaware River in Bucks 

 Co., which are the specimens of which the measurements are given above, and 

 to them must be added the four young ones, mentioned above, taken at Shawnee, 

 Monroe Co. All these are much smaller, and are not at all swollen nor subcyl- 

 indrical. The color of the epidermis is greenish with hght brown or yellowish 

 concentric bands, without distinct rays, or else nearly uniformly light brown, 

 darker behind. The larger ones show the thickening of the shell, and all have a 

 more or less distinct tint of salmon in the nacre. 



In the collections of the Philadelphia Academy of Natural Sciences I have 

 seen comparatively few specimens, hardly more than a dozen. The thickening of 

 the margin of the shell is always present, often also the pinkish color of the nacre 

 and the inflation of the valves. The color of the epidermis ranges from greenish 

 yellow to blackish. 



Localities represented in the Carnegie Museum: 



Delaware River, Yardley, Bucks Co.; Shawnee, Monroe Co., Pennsylvania. 

 Timber Creek, Newbold, Gloucester Co., New Jersey (C. H. Conner). 



Localities represented in the Philadelphia Academy: 



Schuylkill River (I. Lea). 



Thorps Mill-Pond, Branchton, Philadelphia (S. R. Roberts). 

 Delaware River, Torresdale, Philadelphia Co., Pennsylvania (S. R. Jacob). 



Channel of Delaware River, about 600 feet off New Jersey shore, in 35-45 feet depth, muddy bottom, 

 " East of North end of Little Tinicum Island " (L. Woolman)."' 



Distribution and Ecology (See fig. 15): Type locality, Pond, Danvers, Essex 

 Co., Massachusetts (Say). 



Simpson (1900) gives the range of this species as: "St. Lawrence-drainage; 

 north to Lake Winnipeg; south in streams flowing into the Atlantic to Virginia." 

 I am unable to substantiate this, and the localities on record only in part confirm 

 Simpson's statement. The question also arises, whether all the citations recorded 

 actually refer to this species. At all events, I seriously question the record "Lake 

 Erie, Port Dover, Canada" (INIarshall, 1895). South of New Jersey and Penn- 

 sylvania I know of no reliable records whatever. 



In Pennsylvania this species has only been found in the neighborhood of 

 Philadelphia, in the Schuylkill and Delaware Rivers, and in ponds. It occurs also 

 on the opposite side of the Delaware in New Jersey. My own locaUties are farther 

 up the Delaware. Not a single specimen has ever turned up in the Susquehanna 



"^ Little Tinicum Island has no north end; probably what is meant is " south of east end." The 

 locality is off Billingsport, Gloucester Co., New Jersey. 



