ORTMANN: monograph of the naiades op PENNSYLVANIA. 303 



from July 30 to October 24, and from May 9 to July 8. The form is bradytictic, 

 two succeeding breeding season approaching each other closely in July, but an 

 interim is apparently present in this month. However, an occasional overlapping 

 of the seasons is not impossible. Surber's notes (1912, p. 7) on the presence of 

 glochidia are fragmentary, but they also indicate a possible overlapping of the 

 seasons. 



Remarks: The taxonomic relation of this form to L. ovata has been discussed 

 above. Both are forms of the same species connected by numerous intergrades, 

 but locally they may be pure. ' The true ventricosa is easily recognized by size, 

 shape, and color. It differs from the allied L. fasciola in size, and in the character 

 of the rays (not interrupted or wavy). From the eastern representatives, L. 

 cariosa and L. ochracea it differs chiefly in size and color. L. orbiculata has a 

 much heavier shell and different color. 



L. ovata ventricosa is very variable in thickness,' shape, and color. There is 

 more or less tendency to form local races. In some creeks it attains giant pro- 

 portions, while in others it has only a medium size. The latter is the case in the 

 mountain-streams (Cheat, upper Loyalhanna, Quemahoning) . 



The typical characters, most of all the color, are best developed in shells of 

 medium size. In the upper Ohio greenish is the prevailing tint of the epidermis, 

 which is also glossy; though in old shells the epidermis frequently is discolored 

 and loses its gloss, such shells appearing dull brownish or even blackish. On the 

 average the greenish epidermis and the dark rays give to the shell a comparatively 

 dark aspect, but specimens with light yellowish green or light brownish epidermis, 

 and without rays, are not infrequent. If the nacre is strongly tinted with pink, 

 this color sometimes influences the outer color in young specimens, which appear, 

 reddish brown. A peculiar local race has developed in Lake Erie, and will be 

 discussed below. 



With regard to the convexity of the valves and the inflation of the beaks, the 

 Pennsylvanian form varies a little, but not so much as in the southern and western 

 sections of its range. In the South, it is represented by a form with much inflated 

 beaks {satura Lea) which also often has a very dark blackish epidermis. 



Localities in Pennsylvania represented in tlie Carnegie Museum: 



The Ohio and its smaller tributaries: 

 Ohio River, Smith's Ferry, Cook's Ferry, Shippiugport, and Industry, Beaver Co.; Coraopolis (S. N. 



Rhoads), Neville Island, and Edgeworth (G, H. Clapp), Allegheny Co. 

 Little Beaver Creek, Cannelton (Miss Vera Wliite; H. H. Smith), Darlington, and New Galilee, Beaver 



Co.; Enon Valley, Lawrence Co. 



