Maryland Geological Survey 423 



The spiral cones are comparatively large and have seven volutions of the 

 band. The descending lamella are very wide and are devoid of lateral 

 processes or remnants of a connecting loop. 



This species is readily recognized by the \evy high ventral fold with 

 its narrow or linear sinus, and the flat dorsal shell with its very wide and 

 deep sinus in the bottom of which there is a depressed plication. 



This species is common in the upper half of the Oriskany, but does not 

 appear to be gathered often because the valves are nearly always separated 

 and attached to rock. Mr. Andrews found it commonly in the quarries, 

 now abandoned, in the city of Cumberland. 



Length 1.5 cm. ; width 2.1 cm. 



Occurrence. — Oriskany Formation, Ridgely Member. Knobly 

 Mountain and Williams Road near Cumberland, Collier^s Run. 



Collections. — Maryland Geological Survey, American Museum of 

 Natural History, U. S. National Museum. 



Family SUESSIIDAE 



Genus CYRTINA Davidson' 



Cyrtina rostrata (Hall) 



Plate LXXI, Figs. 10-16 



Cyrtia rostrata Hall, 1857, Tenth Ann. Rept. N. Y. State Cab. Nat. Hist., p. 64. 

 Cyrtia rostrata Hall, 1859, Nat. Hist. N. Y., Pal., vol. iii, p. 429, pi. xcvi, figs. 



1-6; pi. xcviii, figs. 8a-8&, 1861. 

 Cyrtina rostrata Hall and Clarke, 1893, Nat. Hist. N. Y., Pal., vol. viii, pt. ii, 



pi. XXV, figs. 1-8; pi. xxviii, fig. 6. 

 Cyrtina rostrata Weller, 1903, Geol. Surv. N. J., Pal., vol. iii, p. 330, pi. xlii, 



figs. 23-25. 



Description. — " Shell semicircular or triangular : ventral valve much 

 elevated at the beak, a distinct sinus extending from beak to front ; beak 

 simple, angular, not incurved: dorsal valve depressed convex, semi- 

 circular; mesial fold moderately elevated, slightly flattened and marked 

 with a faint, longitudinal, depressed line; beak scarcely elevated above 

 the cardinal margin ; hinge-line straight, equalling the greatest width 

 of the shell; area broad triangular, plane, or rarely subarcuate; foramen 



' For an excellent description of this genus, see Hall and Clarke, Nat. Hist. 

 N. Y., Pal., vol. viii, 1893, pt. ii, pp. 43-46. 



