Cladodont Sharks. — Clay pole. 331 
end is lacking. The head shows, so far as can be determined, 
little of that constriction or neck that is so plainly marked in some 
of the other species. Its length from the snout to the front line 
of the pectoral fins is less than in M. clarJci. But the pectoral 
fins are larger and more powerful than there, measuring from tip 
to tip at least twenty-four inches. In other details also we find a 
noteworthy diflference. The mandible is only four and a half 
inches long, or about half as long as in the other species, and the 
teeth were apparently set in a circular form. Thej- are of the 
general form of the t3'pe with one slightl}' curved median cusp and 
a base extended on the inner side, but they are more slender 
than in M. clarki and are not striate. Kemnants of the e3"e cap- 
sules are visible, as in some of the other species. 
The most striking character of the specimen and the one which 
most readily distinguishes it from all the others is the great 
strength of the ventral fins, whence comes the specific name. In 
none of the others are these organs more than just visible, whereas 
here the}' equal the pectorals in solidity though not in size. 
They are short and rounded and contain about twelve strong bony 
rays largest in the middle. 
On the whole these characters seem to warrant a distinction and 
I therefore propose to call it Monocladus pinnatus. 
It is not probable that in all details the outlines here given are 
minutely correct. Pressure and mineralization have doubtless 
somewhat modified the shape of these fishes, but I have considered 
it advisable to represent them as they appear rather than to at- 
tempt au}' restoration beyond the eflfacement of slight obvious im- 
perfections especially in the margin. Beyond question future re- 
search and better specimens will introduce changes and improve- 
ments. But I think all the species here named can be differenti- 
ated b}' characters that can be readil}' recognized where the organs 
are present. 
I will not here enter on the discussion of the man}- interesting 
and important questions connected with the discovery of these 
cladodont fishes. This must be deferred to a future number of 
the American Geologist, as also the consideration of some 
other material less distinct and less fullv examined. 
