118 PALEONTOLOGY OF ILLINOIS. 



crossed by rounded stria* about half the diameter of the rays, 

 giving a strong reticulated character to the surface where the 

 test is well preserved. 



Length 2% in., greatest breadth 2% inch., length of hinge line 

 about 1% infix's. 



Position and locality: St. Louis limestone, Hardin county, 

 Illinois. 



Collector, A. H. Worthen. 



No. 2951 of the Illinois State Museum. 



AVICULOPECTEN MAC-VVHORTERI. (sp. nOV.) 

 PI. XXII, Fig. 4. 



Shell of medium size, inequilateral; obliquely sub-circular in 

 outline, a little broader than long; hinge line about equal to 

 the greatest breadth of the shell. 



Left valve moderately convex, in the umbonal region, and 

 flattened towards the lateral and basal borders. Anterior ear 

 narrow, and clearly defined: posterior ear broader, and not 

 clearly defined from the postero-lateral border, and both orna- 

 mented with rounded striae, similar to those on the body of the 

 shell. 



Surface of the valve ornamented with about sixty to sixty-four 

 rounded striae, each alternate one smaller than the others, and 

 becoming obsolete about half way from the basal margin to the 

 hinge line. 



Length 1% inches, greatest breadth 1 11 / 10 inches. 



Position and locality: Kinderhook group, Kinderhook, Pike 

 county, 111. 



Dedicated to Tyler McWhorter, Esq., of Aledo, Mercer county, 

 111., in consideration of his meritorious services as an industrious 

 collector of western fossils. 



Collector, A. H. Worthen. 



No. 2583 of the Illinois State Museum. 



