Maryland Geological Survey 289 



mediate spaces are regularly cancellated by short revolving striae which 

 hardly rise so high as the transverse ones, giving the entire siirface a 

 pitted or finely reticulate character; approaching the margin, the spaces 

 between these striae diminish, as the result of the rate of growth in the 

 shell, and they often become so crowded as to present the character of 

 simple undulating granulose lines of growth; the striae are not curved 

 in passing over the rounded carina ; when the shell is partially exfoliated 

 they give a lamellose-striate character to the surface. The fossil is 

 usually found in the condition of casts of the interior, which preserve 

 some marks of the transverse striae, but the exterior shell is rarely seen." 

 Hall, 1879. 



There are internal impressions in the Maryland Collection which 

 are referred to this species. The dorsum is conspicuously subcarinate, 

 the transverse striae are clearly shown and are crowded toward the front 

 of the shell, while the revolving striae are rather faintly shown on the 

 upper part of one specimen. 



Length of largest specimen, about 22 mm. ; width, about the same. 



Occurrence. — Eomney Formation, Hamilton Member. About 4 

 miles north of Oldtown on road east of Pine Hill; B. & 0. E. E. cut at 

 21st Bridge; on JSTational Eoad in Gilpin. 



Collections. — Maryland Geological Survey; American Museum of 

 N'atural History. 



Family TURBINIDAE 



Genus CYCLONEMA Hall 



Cyclonema hamiltoniae Hall ( ?) 



Cyclonema Jiamiltontae Hall, 1861, Descriptions of New Species of Fossils, 



etc., p. 19. 

 CycT.onema liaviiltoniae Hall, 18C2, Fifteenth Rep. N. Y. State Cab. Nat. Hist., 



p. 47, pi. V, fig. 16 (not 15). 

 Cyclonema hamiltoniae Hall, 1879, Pal. N. Y., vol. v, pt. ii, p. 37, pi. xii, figs. 



34-36. 

 Sphaerodoma hamiltoniae Grabau and Shlmer, 1909, N. Am. Index Fossils, 



vol. i, p. 701. 



Description. — "Shell subglobose-conical ; height a little more than the 

 width across the last volution; volutions four or five; apex minute and 

 19 



