116 University Geological Survey of Kansas. 



Range and distribution : Upper Coal Measures ; Leaven- 

 worth, Wyandotte county. 



Specimens are abundant in the shales at Topeka which may 

 belong to this species or to A. whitei. The material in hand is 

 too poor to assign with certainty to either species. The proba- 

 bility is, however, that they belong to A. whitei. 



This species can be easily distinguished from A. occidentalis 

 by its smaller size, thinner shell, and the fact that the posterior 

 ear is not so distinct and the shell is less elongate vertically. 



Aviculopecten interlineatus. Plate XIII, fig. 6. 



Avieulopecten interlineatus Meek and Worthen, Proc. Acad. Nat. Sci. 

 Phil., p. 454, (1860): Geol. Surv. 111., n, p. 329, pi. xxvi, ff. 7a, b, text 

 fig. (1866): Whitfield. Ann. N. Y. Acad. Sci., v, p. 694, pi. xvi, ff. 10, 

 11, Q891); Keyes, Geol. Surv. Mo., v, p. 112, pi. xlii, f. 6, (1894); 

 Whitfield, Geol. Sury. Ohio, vn, p. 489, pi. xn, ff. 10, 11. 



Avieulopecten ? interlineatus White, U. S. Geog. Surv. West 100 Mer., 

 iv, p. 149, pi. xi, f. 3, (1877): 13th Ann. Rep. Ind. St. Geol., p. 145, pi. 

 xxx, f. 9, (1884). 



Meek and Worthen's description : " Shell (left valve) rather 

 small, compressed, broad ovate or subcircular exclusive of the 

 ears, not oblique ; length and breadth nearly equal ; hinge 

 straight, about equaling the greatest breadth of the valve 

 below, ranging at right angles to the vertical axis of the shell. 

 Base regularly rounded ; posterior and anterior margins 

 rounded from below the ears to the base. Anterior ear tri- 

 angular, flattened so as to be xevy distinct from the umbonal 

 slope ; posterior ear somewhat larger than the other, com- 

 pressed, triangular, the hinge side being longer than either of 

 the others, rather acutely angular at the extremity. Beak com- 

 pressed, a little nearer the anterior than the posterior extremity 

 of the hinge ; umbonal slopes diverging from the beaks at an 

 angle of about 78°; anterior one subangular. Surface orna- 

 mented by about fifteen regular, very prominent, slender, and 

 obscurely crenulated concentric costa\ which are separated by 

 spaces from four to six times their own breadth, excepting on 

 and near the ears ; spaces between the cosUe occupied by numer- 

 ous fine, regular, closely arranged concentric striae, which are 

 crossed by faint indications of radiating ribs. Diameter, from 



