202 THE DEVONIAN OF MISSOURI. 



Description — This species is represented by an incomplete shell whose surface is 

 marked with regular, simple plications of which there are 6 in the sinus, and about 23 

 on each side of the sinus which is well-defined — the fold on the dorsal valve is indis- 

 tinct. 



Family Meristellidae 



Genus Nucleospira Hall 



Nucleospira ventricosa Hall 



Plate 52, figures 21-33 



Spirifer ventricosa Hall, 1857, 10th Ann. Rept. N. Y. State Cab. Nat. Hist., p. 57. 

 Nucleospira ventricosa Hall, 1859 l Pal. N. Y.„ vol. Ill, p. 220, pi. XIV, figs, la-h; pi. 



XXVIIIb, figs. 2-9, 14, 1861. 

 Nucleospira ventricosa Hall and Clarke, 1893, Pal. N. Y., vol. VIII, pt. II, p. 145, figs. 



128-130; pi. XLVIII, figs. 2-6, 18; pi. LXXXIV, figs. 39, 40, 1894. 

 Nucleospira ventricosa Weller, 1903, Pal. N. J., vol. Ill, pp. 290, 316, pi. XXX, figs. 



19-22; pi. XXXVII, fig. 16. 

 Nucleospira ventricosa Shimer, 1905, N. Y. State Mus., Bull. 80, p. 255. 

 Nucleospira ventricosa Clarke, 1908, N. Y. State Mus., Mem. 9, pt. 1, p. 110. 

 Nucleospira ventricosa Schuchert, 1913, Md. Geol. Surv., L. Dev., p. 430, pi. LXXIII, 



figs. 10-12. 



Description — "Shell globose; valves almost equally convex. Ventral valve having 

 a narrow sinus extending down the centre from beak to base; beak projecting above 

 the other, strongly incurved and pointed (in many specimens the beaks are nearly 

 equal). Dorsal valve having a central depressed line, which is less conspicuous than 

 in the opposite valve; false area very small, concave Surface marked by concentric 

 lines of growth; and, when perfect, covered with minute hair-like spines, which, when 

 removed, leave a punctate surface 



''[Remarks] — The interior of the dorsal valve shows a faintly defined muscular 

 area, a longitudinal septum, and prominent recurved cardinal process, with an accessory 

 process on each side for the attachment of the spires. The ventral valve shows a longi- 

 tudinal septum similar to that of the opposite valve, with a more or less strongly defined 

 muscular depression; area, or false area, a concave triangular space, over which the 

 acute beak is arched. In well-preserved specimens, the beak appears to be minutely 

 perforate upon the under side. Internal spires * * * * showing ten or twelve 

 turns on each side. * * * ****** 



******** —Hall, 1859. 



Genus Meristella Hall 



Meristella laevis (Vanuxem) 

 Plate 52, figures 34-44; plate 53, figures 1, 2 



Atrypa laevis Vanuxem, 1842, Geol. N. Y., Rept. 3rd Dist., p. 120, fig. 2. 



Merista laevis Hall, 1857, 10th Ann. Rept. N. Y. State Cab. Nat. Hist., p. 94, figs. 1-6. 



Atrypa laevis Rogers, 1858, Geol. Penn., vol. II, pt. II, p. 825, fig. 642. 



Merista laevis Hall, 1859, Pal. N. Y., vol. Ill, p. 247, pi. XXXIX, figs. 3, 4, 1861. 



Meristella laevis Whitfield, 1891, Ann. N. Y. Acad. Sci., vol. V, p. 510, pi. 5, figs. 6, 7. 



Meristella laevis Hall and Clarke, 1893, Pal. N. Y., vol. VIII, pt. II, pp. 75-78, pi. XLIII, 



figs. 3-6; pi. XLIV, fig. 4, 1894. 

 Meristella laevis Keyes, 1894, Mo. Geol. Surv., vol. V, p. 104. 

 Meristella laevis Whitfield, 1895, Geol. Ohio, vol. VII, p. 411, pi. I, figs. 6, 7. 

 Meristella laevis Weller, 1903, Pal. N. J., vol. Ill, pp. 290, 317, pi. XXXI, figs. 1-8; 



pi. XXXVIII, figs. 11-18. 



