70 PALEOZOIC FISHES OF NORTH AMERICA. 
like that or Dinichthys and other members of the same family, viz, the pos- 
terior end is spatulate and smooth, and was once buried in cartilage; the 
anterior end, ornamented and bearing teeth, was evidently exposed. 
CALLOGNATHUS REGULARIS, 0. sp. 
Plate XXVII, Fig. 18. 
Dentary bones one to one and a half inches long, nearly straight, 
slightly curved upward at the anterior extremity, which is obliquely rounded; 
posterior end broader, thin, smooth, rounded, spatulate, as in all the Di- 
nichthide; upper margin of dentary bone ‘set with closely approximated, 
cylindrical, blunt-pointed teeth. 
Only two of these little jaws and no other portion of the fishes which 
bore them have yet been found. These are, however, so clearly defined, 
and so distinct from any other fish jaws known, that it has seemed best to 
describe and name them. Their most obvious character consists in the very 
regular and uniform row of teeth with which the upper margin of the den- 
tary bone is set. I know of no other fish jaws which have teeth so uniform 
in size and so closely set. 
Formation and locality: Huron shale; Delaware, Ohio. Collected by 
Rev. H. Hertzer. 
CALLOGNATHUS SERRATUS, 0. Sp. 
Plate XXVII, Figs. 16, 17. 
Dentary bone two inches in length, posterior half spatulate, anterior 
half long-triangular in outline; anterior end rounded, upper margin nearly 
straight, and bearing about twenty closely approximated, compressed, coni- 
cal, lancet-shaped teeth, inclined backward, and increasing in size from front 
to rear; exposed surface of mandible ornamented with irregular longitudinal 
raised lines of enamel. 
I have somewhat doubtfully associated the little jaw described above 
with those found by Mr. Hertzer in the Huron shale at Delaware, Ohio, and 
future discoveries may show that they should be referred to different genera. 
The dentary bones have approximately the same form and ornamentation, 
the upper margin of the anterior half in both is set with teeth, which are 
