418 
PALAEONTOLOGY OF NEW-YORK. 
Fig. 2 e, A cast taken from the impression of a dorsal valve in sandstone. 
Fig. 2/. An impression of the dorsal valve in sandstone. 
Fig. 3. A cast in sandstone of the ventral valve. The specimen has been weathered, and the 
. parts are not as salient as they otherwise would be. The hinge-line is obliterated 
in the specimen. 
Other specimens of the casts, and the separate valves of the species, more recently obtained, 
have served to illustrate more fully the characters here represented but imperfectly. 
Geological position and localities. In the Oriskany sandstone : Albany and Scho¬ 
harie counties (New-York), and Cumberland ( Maryland ). 
Chonetes complanata. 
Plate XCIII. Fig. 1 a, b, c, d. 
Chonetes complanata : Hall, Regents’ Report for 185Q, p. 54; Palaeozoic Fossils, 1857, p. 14. 
Shell transverse, longitudinally semielliptical, about two-thirds as long 
as wide. Ventral valve flat or concave. Dorsal valve unknown : tubular 
spines of the cardinal margin directed obliquely outwards. 
Surface marked by fine closely arranged bifurcating striae, which appear 
to have been crenulated by closely arranged concentric striae. Some of 
the specimens show distant imbricating concentric lines of growth : 
interior striato»granulose ; muscular impression large, not strongly 
marked. 
All the specimens seen of this rare species consist of internal and external casts 
of the ventral valve, from which it is impossible to make out a complete description. 
The few remaining impressions of the row of tubular spines along the cardinal 
margin are barely sufficient to show the presence of these appendages, and do not 
clearly indicate their number, length, curvature, etc. It may be recognized by its 
extreme flatness, finely striated surface, a few distant laminse of growth, and great 
proportional width. 
Fig. 1 a. An impression of the outside of the ventral valve of this speoies. 
Fig. 1 b- A similar impression in sandstone, showing the coneentrio lines of growth, 
Fig. 1 c. A cast of the interior of a ventral valve, showing the muscular impression and 
cavities of the dental lamellae. 
Fig. 2 c (in centre of plate, by error for Id). An enlargement of the imprint of the surface, 
as sometimes seen in sandstone. 
Geological position and locality. In the Oriskany sandstone : Albany and Scho¬ 
harie counties. 
