116 PALEONTOLOGY OF ILLINOIS. 



yond the cardinal border. Anterior ear broken away, posterior 

 ear small and ornamented with fine lines of growths. Surface 

 of the valve ornamented with 36 to 40 radiating unequal-sized 

 costae the alternating ones nearly twice as wide as the others, 

 and all traversed for more than half their length by smaller 

 costoe which become obsolete before reaching the cardinal bor- 

 der. Traces of numerous transverse striae are also visible where 

 the surface of the shell is well preserved. 



Length 2% inches; breadth 2% inches. 



This shell is closely allied to A. provifk'iisis, Cox, sp. from 

 the Coal Measures of Kentucky, but differs from that in its 

 smaller and more numerous costap and transverse striae. 



Position and locality: Lower division of the Chester lime- 

 stone, Chester, 111. 



Collector, Mrs. J. C. Salter. 



No. 2507 of the Illinois State Museum. 



AVICULOPECTEN SPINULIFERUS. Meek and Worthen. 



Pf XXII. Pig. 1. 



Aviculopecten spinuli ferns , Meek and Worthen. 1870, Pro. of the Acad. of Nat. Sc., Phila., 

 and Bulletin No. 2 of the Illinois State Museum of Natural History, page 20. 



Shell of medium size, inequilateral, obliquely ovate; left valve 

 moderately convex, and ornamented with about fify angular 

 spiuuliferous costoe, each alternate one being about twice as large 

 as the others, the small ones coalescing with the large ones 

 before reaching the cardinal border. Beak moderately elevated, 

 and located about one-third nearer the anterior than the pos- 

 terior termination of the hinge line. Anterior ear sharply tri- 

 angular, about half as large as the posterior, and ornamented 

 with three or more spiniferous costae similar to those on the 

 body of the shell. Posterior ear large and not clearly defined 

 from the lateral border, the spiuiferous costae extending without 

 interruption to the cardinal border. Anterior lateral border 

 neatly rounded from the sinus below the ear to the ventral border. 



Length measuring obliquely from the beak to the basal mar- 

 gin l^/io inches; breadth 1% inches; length of hinge line 1% 

 inches; posterior ear 15 / le inch; anterior ear J1 / 1( . inch. Right 

 valve unknown. 



Position and locality: Keokuk shale, Crawfordsville, Indiana. 



Collector, Frank H. Bradley. 



No. 2508 of the Illinois State Museum. 



