ARCTIC ORDOVICIAN AND SILURIAN CEPHALOPODS 275 
11. Kionoceras trentonense Sp. nov. 
Plate XXXF, fig, 1 
, Orthoceras laqueatum (Hall), Pal. New York, 1, 1847, p. 
206, pi. 56, figs. 2 b, c. 
Apical angle about 3 degrees. Diameter at top of specimen 
estimated at 5 mm. Length of specimen 22 mm. At the smaller 
end of the specimen a septum terminates the specimen. That 
part of the specimen which in Hall’s figure extended beneath 
this septum consisted of nothing but matrix. The siphuncle, 
at its passage through the septum, is small and slightly excentric 
in position. The surface of the shell is occupied by about 20 
primary vertical ribs and an equal number of almost equally 
prominent secondary riblets which alternate with the primary 
ones. Both ribs and riblets rise acutely above the general sur- 
face of the shell. In the grooves between the ribs and riblets 
there are additional and much finer striae, usually 3, sometimes 
4 or 5 in number, and visible only under a lens. Finally, the 
microscope reveals numerous very fine transverse striae, about 
70 in a length of 1 mm. These striae are horizontal along the 
left third of the exposed part of the shell, they curve rather 
strongly downward along the middle third and become horizontal 
again along the right third. It is assumed that the right third 
of the exposed part of the shell is the ventral side, and that there 
was a distinct hyponomic sinus whose depth is indicated by the 
amount of deflection of the transverse striae. 
Locality and Horizon. — According to Hall this specimen is 
from the middle portion of the Trenton at Middleville, New York. 
The specimen is numbered 802 A in the American Museum of 
Natural History in New York city. 
Remarks. — The Trenton species here described differs from 
typical Orthoceras laqueatum from the Beekmantown in its 
much smaller apical angle. It is probable that if more were 
known of the surface markings and internal structure of both 
forms that other differences would be noted. 
A similar specimen, from the Leray member of the Lowville 
at Banquette Rapids in Ontario, has 3 camerae in a length 
