2l6 



NORTH AMERICAN INDEX FOSSILS. 



Fig. 258. Stropheodonta pater- 

 soni, pedicle valve. (After Hall.) 



the hinge line and incurved. 



sides and front. The striae are distant and elevated with many 

 finer ones between. Strong wrinkles cross concentrically over 

 the fine striae, being interrupted by the larger ones. 



Oriskany-Onondaga of New York, 

 Ohio, Illinois, Nevada, Ontario. 

 79. S. inaequiradiata Hall. (Fig. 

 259.) Devonic. 



Pedicle valve somewhat gibbous, 

 often arching regularly from beak to 

 front and depressed or concave be- 

 tween the umbo and the cardinal ex- 

 tremities which are somewhat pro- 

 longed. Beak a little elevated above 

 Surface covered with striae, those on 

 the pedicle valve being often coarse, uneven and somewhat fas- 

 ciculate ; those on the brachial valve are more uniform, the 

 stronger ones being distant and sharp with wide interspaces 

 covered with very fine regular striae. 



Onondaga of New York, Ohio, 

 Nevada, Quebec. 



80. S. hemispherica Hall. (Fig. 



260.) Devonic. 



Form, size and general charac- 

 ters similar to 5. concava from 

 which it differs in having the sur- 

 face striae fine and nearly uniform, 

 instead of alternating ; generally 

 also somewhat more convex than 

 6". concava. 



Schoharie and Onondaga of 

 New York and equivalent horizons 

 of Ohio, Indiana, Kentucky, and 



UntariO. Fig. 259. Stropheodonta inequiradi- 



„ „„ .. ,„. „ . ata, with enlargement of interior of bra- 



81. S. concava Hali. (Fig. 261.) chi ; lvalve . 



Devonic. 



Large, with very convex pedicle valve. Cardinal areas high, 

 almost at right angles to each other. Surface marked by strong 

 sharp striae with finer ones between, all crenulated by concentric 

 striae. Profile more concave than that of S. demissa. 



Onondaga and Hamilton of New York. 



