Maryland Geological Survey 379 



Description. — " Shell ovate varying to elliptic and obovate, not sinuate 

 on either valve; old specimens sometimes very gibbous, but generally 

 compressed towards the anterior border in young individuals; valves 

 nearly equally convex; ventral valve most elevated near the middle and 

 towards the umbo; beak pointed, subangular along the lateral slopes, 

 arched or closely incurved ; foramen narrow, and extending nearly or quite 

 to the apex of the beak: dorsal valve slightly less elevated and a little 

 shorter than the opposite ; beak not projecting, incurved. Surface marked 

 by twelve to twenty-eight coarse obscure radiating strijB, crossed by fine 

 indistinct lines of growth, and sometimes near the border by a few strong 

 concentric undulations. The radiating stria; are usually obsolete on the 

 upper half of the shell." Hall, 1857. 



This species, like all the Rensselgerias, varies considerably iji form, in- 

 curvature of the ventral beak, and the degree of striation. However, the 

 small size, nearly constant elongate form, and the incipient striation dis- 

 tinguish this species from those of the higher formations. 



A variety occurring in the Keyser member at Tonoloway bears much 

 more strongly developed plications than the typical form. 



Length 10 mm. ; width 9 muL 



Hall cites this species as from the N'ew Scotland of New York, but 

 most of the material from that State seen by the writer is from the Coey- 

 mans. As a rule, it is one of the characterizing fossils of the last-named 

 zone, but besides its New Scotland occurrence, it is also known in very 

 small specimens in the Keyser at New Bloomfield, Pennsylvania. 



Occurrence. — Heldeebeeg Formation, Keyser Member. Keyser, 

 West Virginia; at Miller's Spring near Cumberland, Corriganville, Tonol- 

 oway, Maryland. New Scotland Member. Near Cherry Eun, West 

 Virginia. 



Collection. — U. S. National Museum. 



Eenssel2Eria subglobosa Weller 

 Plate LXVI, Pigs. 10-12 

 Rensselwria suhglobosus Weller 1903, Geol. Surv. N. J., Pal., vol. iil, p. 329, 

 pi. xlii, figs. 11-18. 



Description. — " Shell subglobular in form, longer than wide. Pedicle 

 valve strongly convex, its greatest elevation near the middle, sometimes 



