548 Contributions to Invertebrate Palseontology. 



rowed toward the peduncular niarg-in, and l)roadest forward of the 

 middle. Foramen c'omi)aratively small, narrowly elliptical, not ex- 

 tending quite to the nuirg-iu, the inner end not reaching- to the c(!ntre 

 of the disk; the point of origin on the valve being slightly excen- 

 tric. Surface marked by fine, not closely arranged, elevated, con- 

 centric lines. 



The specimen described and figured very closely resembles the 

 New York species above cited ; so nearh^ so in fact as to preclude 

 the possibility of detecting specific diflFerences. The specimens froiii 

 New York differ greatly among themselves in the general form and 

 outline of the valves; so that on this character alone it would not 

 be safe to relv ; and the general features of the shell, so far as can 

 be determined from a single valve, are the same in both cases. 



Formation and Locality. — In the brown shales at the top of the 

 Upper Helderli^rg limestone near Dublin, Ohio. 



Genus CHO\ETES Fischer. 



Clionetes scitiila. 



Plate XI, fig. 10. 



Chonetes scitula Hall, Pal. N. Y., vol. 4, pt. 1, p. 130, pi. 21, fig. 4. 



Shell small and semicircular in outline, or in some cases semi-ovate being a 

 little more than half of a circle. Ilinge-line as long or a little longer than the 

 shell below, and but slightly mucronate at the extremities. Ventral valve 

 nearly equally convex or a little depressed just within the cardinal extremi- 

 ties. Dorsal valve flattened or slightly concave. Surface marked with about 

 sixty, fine, even stri;e in the larger specimens, as counted on the ventral valve, 

 and the hinge-line bears three short spines on eacli side of the beak. 



The specimens being in limestone are all much exfoliated, so that 

 the surface striae are not distinctly shown toward the cardinal bor- 

 ders. The shells arc perhaps a little longer than the more typical 

 forms of C. scitula as they occur in the Hamilton shales near 

 Cayuga Lake, N, Y., and are somewhat intermediate in this respect 

 between those and C. Yandelli Hall, from the hydraulic limestones 

 from near Louisville, Ky. 



Formation and Locality. — In thin-bedded bituminous limestones 

 of the Marcellus shale, above the " Bone-bed" at Smith and Price's 

 quarries, near Columbus, Ohio. 



