34 C. R. EASTMAN 
_ The cutting edge of the mandible is beveled to a sharp 
edge, and shows the usual indications of wear. It belonged to 
an average or slightly undersized individual, judging from the 
proportions of a dozen crania that have been found at Milwau- 
kee. The largest of these, it should be noted, is only one fifth 
smaller than an averaged-sized head of D. terreli. The premax- 
illaries and shear-teeth do not call for any special comment, 
except that the latter are without denticles on the posterior 
margin. — 
2. D. halmodeus (Clarke).—The presence in the type speci- 
men of functional premaxillary teeth, and of a carinal process 
on the under side of the dorso-median, are sufficient reasons for 
transferring this species from Coccosteus to Dinichthys. The 
_~mandibles, which measure about 6.5™ in length, have in place of 
a cutting edge a series of seven or more backwardly directed 
denticles. The anterior beak is missing in both mandibles, and 
the premaxillaries are also damaged. The latter are relatively 
very powerful, and provided with an elongated base for attach- 
ment to the visceral surface of the cranium. The plates desig- 
nated as 2, mx, pmx, and fio, in Dr. Clarke’s diagram®* are all | 
parts of a single element, the suborbital. Examination shows 
that the cranial osteology and structure of the dorso-median are 
normal in every way. 
3. D. herzert Newb.— This species is commonly supposed to 
be limited to the Huron Shale, but it probably had a continuous 
range from base to summit of the Ohio Shale. Its occurrence 
in the Cleveland Shale may be strongly suspected, if indeed it is 
not proved by two specimens described by E. W.Claypole. The 
first is the fragmentary mandible known as D. keplert Cl.,? and 
the second is the series of massive plates (plastron and clavicu- 
lar) preserved in the Ohio State Museum, and figured in part in 
Vol. VII of the Ofzo Geological Survey Reports (P\. XX XVIII-XL). 
The clavicular and postero-ventro-median each have a length 
of aboute50™, and the postero-ventro-laterals are over 76°™ 
* Thirteenth Ann. Rep. State Geol. N. Y., Vol. I, 1893, p. 162. 
2Amer. Geol., Vol. XIX, 1897, p. 322, Pl. XX. 
