IIki 1)i:i;ki:i;(; Fok.maiion in Mauvi.am) 37 



A'entral valve convex, gibbous, greatest convexity about one-tliird the 

 distance from the beak to the front ; beak pointed and prominent, strongly 

 iiunirvetl over that of the dorsal valve. In some individuals there is a faint 

 undefined shallow sinus which may extend from the beak to the front, 

 producing at the front a slightly emarginate appearance. Dorsal valve con- 

 vex, less so than the ventral valve, approaching to depressed convex, point 

 of greatest convexity about one-third the distance from the beak to the 

 front; beak prominent and incurved under tliat of the ventral valve. 

 Sometimes an indistinct mesial depression marks the anterior portion of 

 this valve. Surface of both valves marked by indistinct concentric lines 

 of growth which become more prominent towards the front where they 

 become distinct concentric lamellie. 



This species is closely related to N. elegans from which it differs in 

 being less transverse, its outline being more nearly subquadrate. It also 

 differs in the lesser convexity and much less distinct sinus of brachial valve. 



Dimensions : Large individuals IS mm. wide, 16 mm. long. 



It differs from i\'. vcntricosa in being less globose, larger, the ventral 

 valve much more convex than the brachial valve. The valves are of almost 

 equal convexity in Xudeospira venivicosa. 



Length 1.5 cm. ; width 1.6 cm. 



Occurrence. — Heldekberg Fokmatiox, Keyser Member. Cookerly, 

 Devil's Backbone, Cash Valley, Maryland; Keyser, AVest Virginia. 



Collection. — Maryland Geological Survey. 



Family MERISTELLIDAE 



Genus WHITFIELDELLA Hall and Clarke 



WiiiTFiELDELLA ( ?) PROSSERi Grabau 



Plate LXXIII, Figs. 34-3G 



Meristella lavis Whitfield, 1891, Ann. N. Y. Acad. Sci., vol. v, p. 510, pi. v, 



figs. 6 and 7. 

 Meristella la-vis Whitfield, 1895, Ohio Pal., vol. vii, p. 411, pi. i, fif s. 6 and 7. 

 Meristella Iwvis Sherzer, 1900, Geol. Survey Mich., vol. vii, p. 223, pi. xvii, 



figs. 6 and 7. 

 WJiitfieldella cf. hrvis Grabau, 1900, Bull. Geol. Soc. Amer., vol. xi, p. 309, 



pi. xxii, fifrs. 4a-d. 

 Whitfieldella prosseri Grabau, 1910, Michigan Geol. Surv., Publication 2, 



Geological Ser. 1, p. 152. pi. xxi, figs. 3, 8, 9, 12-13; pi. xxx, figs. 6-7. 



