38 MEMOIRS OF THE CARNEGIE MUSEUM. 



QUADRULA PUSTULOSA SCHOOLCRAFTENSIS (Lea) (1834). 



Quadrula pustulosa schoolcraftensis (Lea) Simpson, 1914, p. 850.^' 



Plate III, figs. 6, 7. 



Never before reported from Pennsylvania. 



Characters of variety: Distinguished from typical pustulosa by the more trans- 

 verse and subquadrate outUne. This is brought about by a stronger development 

 of the posterior wing, and the shell thus appears more elongated, and less high. 

 In addition, the posterior ridge appears more distinct, the color of the epidermis is 

 generally lighter, and the nodules are rather poorly developed, but the latter 

 characters are inconstant. 



Size: 1. Erie, Pennsylvania, Cat. No. 61.4515 (old 9 , much L. H. D. 



elongated) 72 mm. 52 mm. 36 mm. 



2. Cedar Point, Ohio, Cat. No. 61.4451 (normal) ... .49 " 41 " 26 " 



Soft parts agreeing with those of the typical form (Ortmann, 1912, p. 251) 

 Glochidia and breeding season not observed. 



Remarks: The characteristic feature of this form, the transverse shape, has 

 been sufficiently emphasized by the earlier authors, but later on it was uncon- 

 ditionally thrown together with pustulosa (Call, 1900; Simpson, 1900). Sterki 

 (1907a, p. 291), however, has again correctly recognized it, and Simpson follows 

 him (1914). I also believe that it is a distinguishable form, but there are inter- 

 grades with the normal pustulosa. In our region, schoolcraftensis is quite distinct, 

 and does not come together geographically with the typical form. But this is 

 the case elsewhere. Baker (1898a, PI. 24 and 25) has given a number of figures, 

 some of which are evidently- pustulosa, but at least one is an undoubted school- 

 craftensis. There are some figures on Baker's plates, which are more or less tran- 

 sitional between the two, and such specimens are also represented in the Carnegie 

 Museum. An example is a fine large specimen from Kishwaukee River, Rockford, 

 Winnebago Co., Illinois (P. E. Nordgren) (L. 64, H. 60, D. 43 mm.). In outline 

 this specimen is intermediate, but on the other hand it is rather smooth and has 

 higher beaks, but not as high as in dorfeuillana. In the latter character it resembles 

 some specimens from the Mississippi, taken at Moline, Rock Island Co., Illinois 

 (P. E. Nordgren) and from Muscatine, Iowa, but the latter are not so transverse. 

 (I have recorded these under pustulosa.) 



Intergrades certainly exist, and as far as I can see at present, they are found 

 in Illinois. They may exist elsewhere. The opinion of Call, Baker, Scammon, 



'- Unio prasmus Conrad, made by Simpson a sj'nonym of typical Q. p^ialulosa, belongs here. 



