214 Xetc iSperic's of Fossils from 01/ io. 



tlu' gemis is known in Anici'ican Devonian rocks, and this cliar- 

 acter, together with its form, its line striae, and its nearly erect 

 slender spines, Avill readily distinguish it from any other species. 

 The dorsal valve above s]ioken of was at first snii])osed to be the 

 young of Stropliodoiita perplana, Conrad's sp., hut the similarity 

 in size and character of stria? to this si)ecies rendei'^ it doubtful. 

 Formation and Locality. — In thin-bedded bituminous lime- 

 stone, from above the "Bone-bed" at Smith and Price's (piarries, 

 near Columbus, Ohio. 



Ptcrinea siiiillis, u. ii^p. 



Pal. O., Ill, Plate 7, Fig. 15. 



Shell small, oblujue; the body, exclusive of the wiiigs, being almost regu- 

 larly although obliquely ovate in outline, the anterior part being the larger ; 

 hinge-line about two-thirds as long as the entire length of the valve ; anterior 

 wing small, distinctly rounded on the end, and separated from the body of 

 the shell, on the left valve, by a distinct sulcus along the surface, and which 

 constricts the margin of the shell ; posterior wing one-third longer than the 

 anterior side, pointed at the extremity and sinuate below. Body of the 

 valve ventricose, stronglj"^ so on the umbone, with a strong tumid beak, 

 Avhich projects distinctly beyond the hinge. Surface of the left valve 

 marked by distinct radii, which are plainly alternated in strength over the 

 body of the valve, but less distinctly so toward and on the wings ; also, by 

 less strong concentric lines, and varices, of growth. Right valve unknown. 



The shell is of the type of Pterinea decussata, Hall, which 

 occurs abundantly in the Hamilton group in New York, but is. 

 of extremely small size, and very ventricose ; the proportionally 

 strong varices of growth showing its adult character. The type 

 is one represented in the Devonian rocks, from the Hamilton to 

 the top of the Chemung, inclusive, in New York, by several dis- 

 tinct species, but which is seldom recognized below this horizon. 

 We may, therefore, consider it as an additional evidence of the 

 age of the beds in which it is found. 



Formation and Locality. — In the thin shaly layers of bitu- 

 minous limestones, from above the "Bone-bed "at Smith and 

 Price's vjuarries, near Cokimbus, Ohio. 



