328 The Americom Geologist. May.ms 
what curved, four inches long by two and a half inches wide at 
base. Rays about six, thinner and fainter than in either of the 
former species. The whole fin indicates less power. ' Branchial 
rays five, well marked. Teeth not j-et known, the reference to 
Cladodus being provisional. No trace of dorsal and but slight in- 
dications of ventral fins can be found. 
The hinder end of the body is horizontall}' expanded as in Cla- 
dodus hepleri, the thin membrauou.s margin resembling in appear- 
ance that of the pectoral fins. The bases of two strong caudal 
fin-rays ai'e visible near the very point of the body, but no other 
indication of the fin can be detected. 
Cladodus rivi-petrosi. 
The total length of this specimen as preserved is between eigh- 
teen and nineteen inches, indicating a fish of twentj'-f our or twent}'- 
six inches in total length. Body three and a half inches wide in 
front of pectorals and widening behind, slightly constricted in 
front of pectorals, from which to the snout it measures four and 
a half inches; snout rounded and blunt. Mandibles elongate and 
narrow, meeting in front and diverging rapidly near the hinder 
end, curving outward. 
Teeth of a strongly cladodont pattern, five preserved in left and 
four in right mandible, showing a median cusp and two lateral 
denticles on each side about one-fourth of the hight of the large 
cusp; outermost largest; median cusp slender, strongly striate to 
tip. 
A second pattern of tooth is shown in the figure, in which the 
median cusp is considerably curved and the lateral denticles more 
spreading. It is also smaller, scarcely exceeding one-half of the 
size of the other. It probably belongs to the other jaw. In 
front of four of these teeth stands another, almost as in Mono- 
cladodus, shorter but otherwise resembling the above. 
There is some doubt concerning the form of several of the teeth 
toward the back of the mouth as the lateral denticles are not well 
shown, but this probably results from imperfect exposure or defect- 
ive preservation. At least it is wiser at present to infer this than 
to insist on their absence. Of branchial rays four only are visi- 
ble, running well forward between the jaws and occupying nearly 
all the space between them and the pectorals. 
Pectorals about three inches long beyond the body and two 
