196 MEMOIRS OF THE CARNEGIE MUSEUM. 



L. H. D. 



Size: 1.(9) 53 mm. 33 mm. 23 mm. 



2 52 " 33 " 24 " 



These are the two largest at hand. 



Soft parts: I have seen only those of a sterile female, and find them identical 

 with those of S. edentulus. Glochidia unknown. 



Breeding season: Conner (1909, p. 112, as Anodonta undulata) found this 

 form gi-avid in December and March, but not in April and May. 



Remarks: For all the material I possess I am indebted to the kindness of Mr. 

 C. H. Conner, who sent me eight specimens, all from the tide- waters of the Dela- 

 ware River, near Newbold, Gloucester Co., New Jersey. These specimens show 

 the differential characters given above. Mr. L. S. Frierson {in litteris) has called 

 my attention to certain supposed differences in the hinge, but I am unable to see 

 them. Moreover the shape of the shell is somewhat variable in the eight specimens 

 at hand, and further I have specimens of the western S. edentulus (chiefly from quiet 

 waters) which come very near to this form from the Delaware in the inflation of the 

 beaks. Further I have certain large and old specimens of S. edentulus, where the 

 inflation of the beaks is much greater than in any specimen from the Delaware. 

 For instance a giant specimen from Cush Cushion Creek (abandoned reservoir) 

 is very remarkable in this respect; but it was found among a large number of 

 typical edentulus and cannot be anything else. 



In the hinge there is the same variation as in S. edentulus. In some speci- 

 mens vestiges of teeth are seen, in others they are almost entirely obliterated, and 

 indicated only by slight thickenings and curves of the hinge-line. Mr. Frierson 

 maintains that the tooth of the left valve (cardinal + interdental) is absent, and 

 represented by an excavation. This does not hold good for all specimens before 

 me, and, on the other hand, this is a condition, very often seen in S. edentulus. 



I am very much inclined to think that this is only a local variety, or even 

 only an ecological race, belonging to the tidewaters of the Delaware River, and 

 localities with a similar environment. In the Delaware, just below Trenton, 

 New Jersey (at Penns Manor, Bucks Co., Pennsylvania) I collected a specimen, 

 which is rather small, and well agrees in outline with the specimens received from 

 Mr. Conner, but the beaks are not inflated and elevated. Specimens from the 

 Delaware River, Trenton, in the Philadelphia Academy, are typical S. edentulus. 

 On the other hand, a specimen of S. edentulus from the Delaware-Raritan Canal, 

 specimens from Conneaut Lake, Lake Erie, and Winona Lake, have the shells 

 inflated more than usual, although the beaks are not so elevated as in the form 

 from the lower Delaware, and thus the outline is more regularly elliptical, and 



