51 



fish has recently been discovered in America, the dentition of 

 which is almost exactly hke tliat of Lejndosircn, except that it is 

 about one hundred times greater. The genus Dinkhthys was 

 founded by Professor Newberry for the reception of this gigantic 

 Placoderm, of which two species at least are recognised and 

 graplucally described by him, in VoL ii. of the State Eeports of 

 the Paljeontology of Ohio. They occur in the Huron Shales of 

 the Upper Devonian series, where they seemed to have pre" 

 ponderated in number, fragments of over a hundred individuals 

 having been detected while the remains of other genera are found 

 more rarely in the same horizon. 



The original specimens of D. TerrelU were destroyed by fire, 

 but fortunately a photograph had been secured from which the 

 plates exhibited were taken. The jaws of this " terrible fish " were 

 each two feet long, the breadth of the head was about tkree feet, 

 imd the cranium was composed of massive bony plates, the solid 

 bone of the occipital portion being three inches in thickness. 



The length of the body is estimated by Professor Newberry 

 to have been about fifteen feet, and its diameter three. The an- 

 terior was protected by huge dorsal and ventral sliields, resembling, 

 in general shape and structure, those of the genus Coccosteus, ren- 

 dered classic by the pen of the lamented Hugh MiUer. Very little 

 is known with regard to the fins, " about six inches only of an 

 apparentlj^ median fin, with well ossified rays as thick as one's little 

 finger," having as yet been found, and, from the absence of scales, 

 it is conjectured that the posterior jiortion of the body of the 

 animal was covered with a tough skin, as in Coccosteus, a genus 

 which possibly protected itself, like the modern sheat fish of the 

 Ganges, by burrowing in the mud, watching for prey with only its 

 mail-clad parts exjjosed. The powerful dentition of Dinkhthys is 

 suggestive of carnivorous habits, and j^robably being so heavily 

 weighted by the thick sliields encasing its vital organs it would be 

 ■compelled to obtain food rather by cunning than by swift piirsuit. 



It is worthy of notice that the ponderously armed Flacoderms 



