190 PALEOZOIC FISHES OF NORTH AMERICA. 
those genera the sockets were deeper and the teeth more firmly fixed in 
them. 
In some respects, therefore, it will be seen that Cwlosteus is allied to the 
Sharks, and it is possible may be found to form a sort of connecting link 
between them and the Ganoids. Of this, however, better proof will be 
needed before it can be made the basis of any generalization. We find 
that the ossification of the skeleton varies considerably among the Elasmo- 
branchs, and the most natural method of increasing the amount of bony 
tissue in the skeleton would be to ossify and indurate the external surface 
of the bones, thus giving them greater strength without adding greatly to 
their weight. Possibly we have in Ce/lostews an example of this stage of 
progress, and without venturing any premature conclusion as to its cause or 
history, I deem it proper to call attention to this particular structure, hoping 
that those who may come into possession of more and better material may 
find an explanation of what is now somewhat enigmatical. 
Of known fossil fishes Calosteus perhaps comes nearer to Pappichtys 
Cope? than any other. Species of this genus have been described by Leidy, 
Marsh, and Cope. They occur in the Eocene rocks of the interior of the 
continent, and have been regarded as closely allied to, if not generically 
identical with, Amia. Should more material show Ce@losteus to be really 
allied to Améa, it would carry back the line of descent of this interesting 
Ganoid much farther than it has before been traced. 
CaLosTEus FEROX, Nl. Sp. 
Plate XXXYV, Figs. 1-4. 
The detailed descriptions of the few remains of this species yet found 
are given in the characters of the genus of which this is taken as the type. 
The specific name is chosen from the truly formidable character of the den- 
tition. The dentary bone was very thick and strong, twelve to fifteen 
inches in length, and carried seven conical teeth, of which the largest were 
fully eight centimeters in length by fourteen millimeters in diameter at the 
middle and two centimeters at the base. Jaws bristling with such teeth 
and moved by the powerful muscles that are shown to have been attached 
1Geol. Survey Territories, vol. 3, book 1, 1884, pl. 3, p. 56. 
