Maryland Geological Survey 431 



specimens the beaks are nearly equal) ; dorsal valve having a central de- 

 pressed line, but less conspicuous than in the opposite valve; area very- 

 small, concave ; surface marked by concentric lines of growth " and, 

 " when perfect, covered with minute hair-like spines, which, when re- 

 moved, leave a punctate surface." Hall, 1857. 



Length 8 mm. ; width 9 mm. 



This species is readily confounded with small N. elegans. The outline 

 and the convexity of the valves are not so reliable for distinguishing this 

 species as is the dorsal elevation along the median portion of the valve. 

 This part in N. elegans terminates in a sinus and is most marked in trans- 

 verse specimens. Common in the JN'ew Scotland member. 



Occurrence.— Helderberg Formation, Keyser Member. Moorefield, 

 West Virginia. Coeymans Member. Devil's Backbone. New Scot- 

 land Member. Cumberland, North Mountain, Maryland ; Cherry Run, 

 West Virginia. 



Collections. — Maryland Geological Survey, U. S. National Museum. 



NucLEOSPiRA elegans Hall 

 Plate LXXIII, Figs. 13, U 



Nucleospira elegans Hall, 1859, Nat. Hist. N. Y., Pal., vol. iii, p. 222, pi. 

 xxviiib, figs. 10, 11, 13 ( ? 12c, 12d, not 14 = N. ventricosa) , 1861. 



Description. — " Shell suborbicular, wider than long. Ventral valve 

 gibbous, particularly towards the umbo, with a flattened or sometimes 

 depressed mesial line down the center: beak elevated above that of the 

 opposite valve, and incurved ; area sometimes well defined. Dorsal valve 

 depressed convex, somewhat gibbous towards the beak, with a narrow de- 

 pressed mesial line above, which becomes a broad depression below, pro- 

 ducing a gentle sinuosity in the outline of the front: beak small, closely 

 incurved beneath the boak of the opposite valve. Surface of shell finely 

 and beautifully punctate, and sometimes preserving remains of pilose 

 covering." Hall, 1859. 



This species, as a rule, is larger and decidedly more transverse than N. 

 ventricosa, and is abundant in the New Scotland member. 



The specimens from the Oriskany are of the transverse variety and are 

 about twice as large as the normal New Scotland individuals. 



