310 
PALAEONTOLOGY OF NEW YORK. 
Genus CHONETINA, Krotow. 1888. 
1884. Chonetella, Krotow (not Waagen). Artinskische Etage, p. 274. 
1888. Chonetina, Krotow. Mom. du Comite G6ologique, vol. vi, p. 500. 
A brief description of the characters of this genus* has been given by 
CEHLERT,f from which it appears that “ Chonetina differs from Chonetes by its 
very convex ventral valve, having a profound sinus; the small valve, very 
concave, follows the curvature of the larger; in the interior of the dorsal valve 
are tubercles arranged in radiating series which unite to form high, compact 
lamellae, extending from the beak to the anterior margin ; two of these, more 
prominent than the rest, limit the surface occupied by the sinus of the larger 
valve. The type, C. artiensis, Krotow, belongs to the horizon of the Artinskian 
grit (Permian).” 
Without actual knowledge of the specimens upon which this separation from 
Chonetes has been based, it may be imprudent to express an opinion as to the 
value of the proposed genus. The American species which are deeply sinused 
on the pedicle-valve, e.g., Chonetes Verneuiliana and Ch. mesoloba, Norwood and 
Pratten, show no valid grounds for separation from Chonetes. 
Genus CHONOSTROPHI A, gen. nov. 
PLATE XV b, FIGS. 14-19; AND PLATE XVI, FIGS. 13,29. 
1857. Chonetes, Hall. Tenth Rept. N. Y. State Cab. Nat. Hist., p. 56. 
1859. Chonetes, Hall. Palaeontology of N. Y., vol. iii, p. 418, pi. xciii, figs. 1 a-d, 2 c. 
1882. Chonetes, Whitfield. Annals N. Y. Academy of Science, vol. ii, p. 213. 
1883. Chonetes, Hall Rept. N. Y. State Geologist for 1S82, pi. xvi, figs. 13, 29. 
Diagnosis. Shell reversed, concavo-convex, the pedicle-valve being slightly 
convex about the umbo, but becoming broadly concave over the pallial region. 
Outline and contour strophomenoid; valves extremely tenuous and compressed; 
surface covered with fine, alternating or fasciculate striae. In the pedicle-valve 
the upper margin of the cardinal area bears a row of hollow spines of the same 
structure and arrangement as in Chonetes. The delthyrium is narrow and 
appears to be more or less completely closed. The teeth are quite strong and 
* The original descriptions of both genus and species are in the Russian language, 
f L’Annuaire g6ologique universel, vol. v, p. 1152. 1889. 
