330 The American Geologist. May, isos 
half inches wide at base, and measuring twenty-two inches from 
tip to tip; fore margin curved backward, thirteen and a half inches 
behind snout; hind margin nearly straight; rays about twenty, very 
strong and bonj^, the longer forking toward the tip; margin mem- 
branous. 
Teeth numerous, well preserved, in two rows as shown in the 
figure, nine in one and five in the other, each consisting of a single 
cusp without lateral denticles, slightly striate below and rising 
from a forking base; base not projecting in front but extending 
backward inwardly as shown. In front view these teeth are 
strongly suggestive of the outline of Lammi., though the resem- 
blance disappears on examination of their bases. 
Striation moderatel}' strong and not as in the former species 
consisting of a merel}' uneven surface ; front face of cusp nearly 
flat; hinder face curved or doubly sloping. 
A peculiar feature of the dentition of this fish is the fact that 
the teeth stand in pairs one close behind the other, as shown in the 
small figure. The outer one is frequently broken, but this has 
evidentl}^ been done during fossilization or extraction. At least 
four of those in the left mandible show this double character, and 
more than one of those on the right side. Some of the front teeth 
show what is apparently a small cusp lying close in the fork of 
the base of the larger one. These do not present the appearance 
of wear or of fracture as is usual in the outer row of the teeth of 
sharks where they are passing out of use, though this is probably 
the explanation of the position of the double teeth at the back of 
the jaw. 
No trace of the membranous expansion near the tail is seen in 
this fossil as in the C. sinuatus, though in this region the slab 
was badly weathered before it was discovered. Its absence cannot 
therefore be inferred. 
The caudal fin is, however, unusually well shown and indicates 
a considerable hindward extension and attenuation of the body. 
Four or five strong fin-rays are visible above and below. 
Monocladodns pinnatus. 
The single specimen representing this species is less perfectly 
preserved than are most of the others, aud were it not for a single 
feature I should hesitate to consider it distinct. In length it ap- 
parently somewhat exceeds Monodadodus clarki, but the hinder 
