CARBONIFEROUS PERIOD. 149 



. Aviculopecten McCoyi Meek and Hayden. 

 Plate XI, tig. 2 a. 

 Aviculopecten McCoyi Meek aud Haydeii, 1864, Palajout. Upper Missouri, 50. 



Left valve moderately convex ; height and breadth apparently about 

 equal ; posterior ear prominent, angular, its outer margin concave, and its 

 surface marked by small, obscure, radiating costse and numerous distinct 

 lines of growth ; anterior ear unknown. Surface of the body of the valve 

 marked by six or eight strong elevated costse, ^vhich have sudden enlarge- 

 ments, at irregular intervals, that are covered by vaulted, scale-like projec- 

 tions, giving the costse a knotted appearance ; the spaces between the large 

 knotted costaj marked by numerous fine, distinct, slightly flexuous, raised 

 stiise, which increase in nmnber by implantation as the shell increases in 

 size; the whole surface is also marked by fine concentric striae and occa- 

 sional coarser imbricating lines of growth. Full breadth of the shell about 

 thi'ee centimeters. Right valve unknown. 



The collections contain only a single imperfect left valve, but its sur- 

 face-features are sufficiently characteristic to indicate its specific identity. 

 In general aspect of the surface, this shell resembles that of Pseudomonotis 

 or Eumicrotis rather more than an Aviculopecten ; but the length of the hinge- 

 line and the character of the posterior ear leave no doubt of its proper 

 reference to the last-named genus, and its surface-markings and form, in 

 addition, leave as little doubt as to its specific identity with A. McCoyi 

 Meek and Hayden. These gentlemen obtained their type-sjDccimens, from 

 stx'ata regarded by them as Permian, at South Cottonwood Creek, Kansas ; 

 while ours is evidently from a lower horizon. 



Position and locality. — Strata of the Carboniferous period ; near Bear 

 Spring, Camp Wingate,'New Mexico. 



Aviculopecten ? interlineatus Meek and Wortheu. 

 Plato Xr, fig. 3 a. 



Aviculopecten interlineatus Meek and Wortbeu, 1860, Proc. Acad. Nat. Sci. Pliila., 454. 

 Aviculopecten interlineatus Meek and Worthen, 186C, Geol. Siirv. Illinois, ii, 329. 



Shell rather small, broadly subovate in outline exclusive of the ears ; 

 breadth nearly equal to the height, slightly oblique, or the axis ahnost at 



