THE 
AMERICAN GEOLOGIST 
Vol. XII. NOVEMBER, 1893. No. 5. 
[Paleoxtological Notes From Bctchtel College.— No. 5. | 
ON THREE NEW SPECIES OF DINICHTHYS. 
By E. W. (lavpole. Akron, O. 
Among the material which lias recently come to hand we have 
the means of denning three new species of Dinichthys by parts 
of their dentition. It seems to the writer on the whole wiser to 
follow this plan than to risk the multiplication of names and 
perhaps synonyms b}* using other parts of the fishes as means 
of defining species, both because these other parts are less 
characteristic and because they are also less frequently found. 
Of the species of Dinichthys thus far discovered the denti- 
tion of the greater number is more or less known, some of 
the teeth having been described in at least eleven of the four- 
teen species hitherto named. It may occasionally be possible 
by a careful employment of tin- process of exclusion to deter- 
mine that a new^form is non-descript, but it is safer to char- 
acterize by the dentition in our present state of ignorance 
regarding the structure of tin- whole of these great placo- 
derms. 
In accordance with this plan, therefore, I here define three 
species of Dinichthys from sonic parts of tin- organs of the 
mouth. 
The first, of which figures are given herewith ( 1>. lincolni) 
is based upon a premaxillary of moderate size, measuring 
about one inch and a half in a vertical and one inch in a hor- 
izontal direction. The angle made by the two limbs, 80 to 
