1885.] NEW YORK ACADEMY OF SCIENCES. 27 



Titanichthys. 



About two years since, Mr. Terrell announced to me the 

 discovery, in tlie^Huron Shale, of the cranium and some otlier 

 bones of a Phicodecm fisli still more gigantic than Diniclttliys. 

 AVhile evidently belonging to the same family, it is generically 

 distinct, and I gave it the name of TitanicMliys. 



As in the former genus, the head is triangnlar in outline, but 

 the largest cranium oi DinicMhys is about three feet broad across 

 the occiput, while the cranium of TitanicldJiys has a breadth of 

 about four feet. 



Tlie cranial surface, as in Dinichthys, is granulated or nearly 

 smooth, and is ornamented with a series of incised lines or 

 grooves, which form a distinct and somewhat graceful pattern. 

 The great dorsal shield is two feet in diameter, rounded in out- 

 line, and, as in Dinichthys, is bordered by quadrangular or tra- 

 pezoidal post-tem])oral ])lates, whicli are fifteen inches in breadth. 

 The cranium found by Mr. Terrell was associated only with the 

 post-temporal and sub-orbital phites; the latter are paddle- 

 shaped, as in DinichtJtys and Coccosteus, and deeply notclied for 

 the eye, which was apparently of large size. 



Within the last three months two or tliree imperfect craniums 

 of Tiianichthys have been found by Dr. AVilliam Clark, of Berea, 

 in the valley of Rocky Eiver; and with these, the dorsal shield 

 and mandibles, before unknown. Tlie latter v.yq about tliree feet 

 in length, the posterior end spatulate, the anterior turned up 

 like a sled-runncr, as in Dinichtliys, but showing no cutting 

 edge or acute point, so that it may be inferred that the jaw was 

 covered with a horny envelope, as in the turtles. 



All the bony plates of Titaniclitliys are apparently thinner 

 than the corresponding parts in Dinichtliys, though of larger area, 

 and the mandibles, though longer, are much more slender. The 

 general plan of structure, however, seems to have been quite the 

 same, though we yet want tlie dentition of the upper jaw and the 

 plastron which covered the ventral surface, in order to make a 

 detailed comparison. 



The only species yet known was described before the Berlin 

 Geological Congress; and, as the most gigantic fossil fish known, 

 it was given the name of the founder of fossil ichthyology, 

 and was called Titanichthys Agassizii. 



Diplognathus. 



In April, 1878, I read before the Academy descriptions of 

 several new fossil fishes, of which the most interesting was called 

 Diplognathus mirabilis, a name chosen to indicate some remark- 

 able features in the structure of the under jaw, the only part 



