24 PALAEONTOLOGY OF OHIO. 



I liave frequently been asked by those examining the bones of Dinich- 

 thjs, what was the probable size of this great fish ? and what inference as 

 to its liabits could be drawn from its remarkable dentition ? 



To these Cjuestions, which will doubtless suggest themselves to the 

 readers of the foregoing pages, I v>-ill attempt such answers as are deduci- 

 ble fi'om the facts in my possession. The size of the two species of 

 Dinitihthij8 was apparently about the same. This we infer from the rela- 

 tive size of the corresponding bones ; the mandibles, for example, having 

 a maximum length of about two feet in both. 



The lengtli of the body cannot be accurately determined from any facts 

 yet obtained, as the caudal extremity w'as provided with no external or 

 internal bony parts, which have been found. In all probability, it was, 

 as in Coccosteus, protected by a leathery skin, and the vertebral column 

 was cartilaginous. 



AVe shall, however, fi-nd some traces of the interspinous bones, and the 

 rays of the caudal fin, by which the length of the body may be ascertained, 

 as has been done in regard to Coccosteus. If we take the proportions of 

 CoccQsteus (the nearest known ally of Diniclitliys) as our guide, we may 

 estimate the length to have been fifteen to eighteen feet, and the diameter 

 of body about three. 



In regard to the habits of Dinichthys, I think we may say with confi- 

 dence that it was carnivorous. This is plainly taught by the dentition of 

 D. Hertzein, in which the mandibles and "maxillaries " are set with sharp 

 teeth, which must have served to hold other fishes, perhaps the smaller 

 ones, brought within the embrace of the formidable jaws. The cutting 

 edges of the mandibles and "maxillaries" of D. Terrelli^ are not so 

 plainly indicative of a carnivorous habit, for some of the turtles are veget- 

 able-feeders, with a dental apparatus similar in form and function too, though 

 homologically different from that of this species of DiniGhthys. Still, the 

 liuge anterior teeth, interlocking to a distance of three or four inches, 

 would hardly have been used for any other purpose than for seizing and 

 holding living, struggling prey. 



As the dentition of Leindosiren is almost precisely that of Dhiichthys, 

 it is doubtless used for the same purposes and in the same way. And 

 since this similarity of dentition indicates a general similarity of habit, it 

 has seemed to me that we might perhaps learn something of the nature 

 of the food of Binichthys, and his mode of seizing and masticating it, by 

 observing the habits of Lejpidosiven. 



The fullest exposition of the anatomical structure of Lejndosiren will be 

 ibund in Owen's Memoir, cited above, but this contains almost nothing in 

 regard to its habits. The most satisfactory description of the life of the 

 animal is furnished by the Eev. J. G. Wood, in his " Natural History." A -• 



