Maryland Geological Survey 435 



plicated; beak of ventral valve straight, extending beyond the opposite, 

 truncated at the apex by a round perforation partly formed by the deltid- 

 ium ; beak of dorsal valve incurved. Surface marked by twelve or thirteen 

 prominent subangular plications, the two central of which, on the ventral 

 valve, are slightly smaller than the others, and a little depressed. These 

 two plications coalesce before reaching the beak : the central plication of 

 the dorsal valve is smaller and a little more depressed than the others, 

 and becomes obsolete before reaching the beak." Hall, 1857. 



Length 11 mm.; width 8 mm. 



Occurrence. — Oriskany Formation, Eidgely Member. Since Hall's 

 description of this species, no other examples have been found. The type 

 specimen is very likely from the Lutheran Church quarry in Cumberland. 



Collection. — American Museum of Natural History. 



Rhynchospira globosa (Hall) 

 Plate LXXIl, Figs. 16-25 



Waldheimia globosa Hall, 1857, Tenth Ann. Rept. N. Y. State Cab. Nat. Hist., 



p. 87. 

 Trematospira (Rhynchospira) globosa Hall, 1859, Nat. Hist. N. Y., Pal., vol. 



iii, p. 215, pi. xxxvi, figs, la-p, 1861. 



Description.- — " Shell subglobose, oval : ventral valve a little larger than 

 the opposite one, most gibbous in the umbonal region; beak prominent, 

 rounded and arched, perforate at the extremity by a round aperture, one 

 side of which is formed by the deltidium : dorsal valve shorter than the 

 ventral; beak incurved. Surface marked by twelve to sixteen somewhat 

 angular plications on each valve, two or three of which are slightly de- 

 pressed on the middle of both valves, so as to produce sometimes a faint 

 emargination in front; the depressed plications smaller than the others, 

 and often becoming obsolete before reaching the beak." Hall, 1857. 



Length 11 mm.; width 11 mm. 



Specimens from the Iveyser member have more numerous and finer 

 plications than the typical form, in which respect they approach B. 

 formosa. The shells are smaller and more globose than in the latter 

 species. 



