' TRENTON LIMESTONE. . 187 



the shell, the detail of the surface markings is partially lost, ami a broad dorsal carina is 

 sometimes all that is observaliie ; I lie marginal carina; are often faintly distinguishable by 

 a slight depression on either side. A section below tjie a])ertnre presents an extremely 

 excentric ellipse, which is depressed on the ventral side by tiic convexity of the contiguous 

 volution. 



Fig. 8 a. Dorsal view of a small specimen, preserving a portion of the shell. 



Fig. 8 h. View of the aperture, which is very imperfect. 



Fig. 8 c. A fragment, showing the carinas and dorsal band very distinctly, d. The same enlarged. 



Fig. 8 e. Cast of a larger specimen, imperfect towards the aperture, and showing only the broad dorsal 



carina. /. Lateral view of the same, showing the umbilicus. 

 Fig. 8 g. Section of the last volution below the aperture. 



Position and locality. This species occurs in the lower shaly portions of the rock at 

 Middleville, and in the compact lower layers of the same rock, immediately above the 

 Black-river limestone, at Watertown, Jefferson county. (State Collection.) 



245. 5. BUCANIA PUNCTIFRONS. 



Pl. XL. A. Figs. 1 a, b, e, d, e. 

 Bellerophon punctifrona. Emmons, Geol. Report, 1842, pag. 392, fig. 5. 



Convolute, suborbicular ; volutions about three, gradually enlarging, rounded upon the 

 back ; dorsal line marked by an abrupt narrow carinal band ; sides of the volutions 

 abruptly rounded, suddenly depressed into a broad deep umbilicus, which reveals the 

 inner volutions ; surface marked by rounded or rhomboidal punctures, which are regularly 

 arranged in lines in two directions ; carinal band marked by close curved striae ; the last 

 volution is little extended, and abruptly expanded near the aperture, which has a shallow 

 sinus on the dorsal margin. 



This beautiful species is readily distinguished by tiie peculiarly ornamented surface. The 

 dorsal band is sometimes abruptly elevated, and at other times even with the surface of 

 the shell, and marked by curved striae. In a single specimen I have detected lateral 

 longitudinal ridges, which interrupt (he regularity of the surface markings ; but these 

 appear to be accidental. 



Fig. 1 a. Dorsal view of a small specimen, h. Lateral view, showing the umbilicus. 



Fig. 1 c. Dorsal view of a larger specimen, showing the elevated carinal band, which docs not rise 



above the surface on the lower part of the shell. 

 Fig. 1 d. Lateral view of another specimen, showing the side of the shell, which is obtusely angular 



with obscure lono-itudinal ridafes. 

 Fig. 1 e. A portion of the surface enlarged. 



Position and locality. This species occurs in the higher crystalline portions of the rock 

 a( Middleville and Watertown. (State Coileetion.) 



24* 



