BEEDK : NEW FOSSILS. 149 



more acute and apparently longer spines. Mr. Butts makes nu men- 

 tion of finer surface-markings. The Topeka specimen is from a much 

 higher horizon. 



Aviculopecten subecmivalvus, n. sp. Plate V, fige. 3, 3a. 



Shell thick, moderately large, subequivalvular, rather convex, quite 

 oblique, ears well developed. The hinge is nearly straight, the beak 

 does not project, the angle of divergence of its sides is about eighty to 

 ninety degrees. The left valve, exclusive of the ears, is ovate ; anterior 

 ear well developed, obtusely angular, marked only by strong lines of 

 growth ; the rise from the ear to the body of the shell is abrupt ; the 

 marginal sinus separating the ear from the rest of the shell broad, 

 shallow, and ill-defined. The posterior ear is unknown. The anterior 

 margin below the ear forms an ovate curve, which is probably con- 

 tinued on the ventral and postero-ventral margins. The surface of 

 this valve is apparently marked only by stronger and fainter concen- 

 tric lines except on the front and back sides, where there are radiating 

 rows of vaulted lamella?. It is entirely probable that these marks 

 once extended over the entire surface, but have been worn off from 

 the more convex portions. Judging from another specimen, the right 

 valve is somewhat flatter than the left and quite as oblique. Posterior 

 ear very small and obtuse ; anterior ear quite large, marked by obscure, 

 large, radiating ribs and probably vaulted lamella?, as well as strong 

 concentric markings; separated from the shell by a deep sulcus. 

 Margin from the beak around the posterior to near the middle of the 

 shell is a regular ovate curve, antero-ventral margin somewhat pro- 

 duced but rounded, extending obliquely toward the beak until the 

 deep byssal sinus is reached. Ornamentation as in the other valve. 

 In this specimen it seems that the radiating rows of scales covered 

 the entire surface before being worn away. Length, o<> mm.: height, 

 32 mm.; hinge, 17 mm.; thickness, about 5 mm. 



Position and locality: Thin limestone, south of Dover. Kan, in 

 Upper Coal Measures. Type in author's collection. 



This shell may prove to be a Pseudomonotis, as the critical charac- 

 ters are not well known. It is not liable to be confused with any 

 other shell from the Coal Measures. 



Pinna lata, n. sp. Plate V, fig. A. 



Shell small for this genus, not very convex, probably plain except 

 the usual growth marks, acutely pointed at the beaks, which are ter- 

 minal. The angle of divergence of the shell is thirty degrees. This 

 species is based on three casts. The type is not distorted, but the 

 posterior end is broken away. There are two other specimens from 



