A Xc>r Titanichthys. — Claypole. 167 
characterize the species as different from all that have been 
hitherto described. 
These mandibles are minute compared with those with 
which the name has been usually associated, showing that 
the genus included species ranging widely in size. Their 
length is on\y five and a half inches. One of them, the left, 
is represented in plate X. It lias the spatulate hinder end 
that marks all the kindred forms, but the front is much 
thicker and less pointed than in either T. <i<i<issi:i, T. clarki, 
T. rectus or T. attenuatus, the only other species yet known. 
No teeth have been found, but the socket or channel in which 
they may have been set is clearly marked and extends along 
about one inch and a half back from the tip, being scarcely 
more than one quarter of an inch deep. The greatest depth 
of the jaw is about one inch from the point and here it does 
not exceed three quarters of an inch. The outer wall of the 
alveolus or channel is, as in the other species that sbbw it. 
higher than the inner. The mandible is scarcely one fourth 
of an inch in thickness at its maximum, which occurs at the 
point of greatest depth, and from this it thins away in both 
directions. 
The above details are amply sufficient to characterize this 
new species, which in consequence of its relatively smaller 
length and the bluntnesss of its anterior extremity I propose 
to name 
Titanichthys brevis. 
But as mentioned above, the slab shows several other plates 
whose connection with the same individual is beyond ques- 
tion. Some of these are represented in the main figure and 
others on the reduced diagram of the head (plate X). The 
supra-occipital, the exoccipital, the large marginal, the frontal 
and the post-orbital can all be distinguished on the chief spec 
imen. Some of them present the inner and others the outer 
surface, having been somewhat displaced before fossilization 
took place. 
A second specimen, showing only the inner face of the cra- 
nium with somewhat less displacement of the corresponding 
plates, confirms the details gathered from a study of the first; 
and the diagram of the head has been compiled from data oh 
tained from both specimens. 
