234 MEMOIRS OF THE CARNEGIE MUSEUM. 



Soft parts (See Ortmann, 1912, p. 325). Glochidia: Lea (Obs. VI, 1858, PI. 5, 

 fig. 18) Ortmann (19116, PL 89, fig. 16). Surbcr, 1912, PI. 2, fig. 18. My measure- 

 ments are: 0.22 X 0.24; those of Surber: 0.220 X 0.260 mm. 



Breeding season: Records for gravid females are rather complete, and cover 

 the period from Aug. 3 to Oct. 24, and from March 21 to May 20. This is a brady- 

 tictic form with the interim in June and July. According to Surber (1912, p. 7), 

 glochidia are present from September to July, with the interim in August (in Iowa). 



Remarks: Externally a form of simple appearance, without striking character- 

 istics. It may be recognized by its large size and heavy shell, of a rather regular 

 subelliptical outline, with more or less distinct, broad rays. Young shells might 

 be mistaken for Eurynia iris, or even for Lampsilis luteola, but these latter are 

 both more elongated, and differ somewhat in color. 



A. ligamentina varies a good deal. The southern variety, gibba of Simpson, 

 is not represented in Pennsylvania. Humped specimens (the character of gibba), 

 are found, but they have the earmarks of cripples. The var. nigrescens (Simpson, 

 1914, p. 82) reported from Allegheny County, is merely an individual variation, 

 which is assumed occasionally by old shells, and does not deserve a name. 



There are peculiar forms in Arkansas, wliich generally go by the name of liga- 

 mentina. They differ from the normal form in the color of the epidermis and of 

 the nacre. I have not made up my mind with regard to these, and in the following 

 list of localities they have been omitted, as has been the var. gibba. Only un- 

 doubted representatives of A. ligamentina are recorded. 



Localities in Pennsylvania represented in the Carnegie Museum: 



Ohio-drainage: 

 Ohio River, Smith's Ferry, Shippingport, Cook's Ferry, and Industry, Beaver Co.; Beaver, Beaver Co. 



(W. E. C. Todd); Dead Man's Ishmd, Shousetowu, and Neville Island, Allegheny Co.; Coraopolis 



(S. N. Rhoads) and Edgeworth (G. H. Clapp), Allegheny Co. 

 Little Beaver Creek, Cannelton, Beaver Co. (Miss Vera White). 



Beaver-drainage : 

 Beaver River, Wampum, LawTence Co. (G. H. Clapp & H. H. Smith). 

 Connoquenessing Creek, Ellwood City, Lawrence Co. (G. H. Clapp & H. H. Smith). 

 Slipperyrock Creek, Wurtemberg, Lawrence Co. 



Mahoning River, Mahoningtown, Coverts, and Edinburg, Lawrence Co. 

 Shenango River, Harbor Bridge and Pulaski, Lawrence Co. 



Allegheny-drainage : 

 Allegheny River, Sandy Creek, Harmarville, and Natrona, Allegheny Co.; Braeburn, Westmoreland Co.; 

 Schenley, Aladdin, Godfrey, Johnetta, Kelly, Rosston, Mosgrove, Templeton, and Parkers Land- 

 ing, Armstrong Co.; AValnut Bend, Venango Co.; Tionesta and Hickory, Forest Co.; Warren, 

 Warren Co. 



