610 GEOLOGY OF OHIO. 



That these three plates are organically related admits of no reason- 

 able doubt. Two of them are still in union and the third cannot have 

 been much if at all displaced. Its position suggests the possibility that 

 it may in life have been united with the branch plate mentioned above 

 whose end indicates such a suture. 



Regarding the position of these bones in the fish we cannot be cer- 

 tain, That the flat plate was external and ventral can hardly be doubted. 

 That the flange and other bones were so is unlikely. Bones so heavy 

 must have served an important purpose in the economy of the animal, 

 and it seems quite legitimate to regard them as the supporting mechan- 

 ism of the fins or locomotive organs whatever these may have been. 



•This reference would bring them into the position of the shoulder 

 or pelvic girdle of one of which they probably are parts. The elements 

 of the former are the scapula, clavicle and coracoid but among these 

 it is not easy to determine which of these is, or are represented. 



The plates have considerable resemblance to one figured by Dr. 

 Newberry, on Plate XL/VIII of the Palaeozoic Fishes, as the clavicle of 

 Dinichthys, though the specimen represented in his figure seems to pos- 

 sess only one of the parts here described. The two are almost equal in 

 size but differ considerably in outline as may be seen on comparison. 

 Though the cranium is not present yet the other plates indicate' that the 

 whole "find" was a specimen of TUanichthys, and we can therefore 

 scarcely do otherwise than consider these three bones as a part of the 

 or pelvic shoulder girdle of that genus. 



Yet the massiveness of these bones ill agrees with the thinness 

 of the armour of the head of Titanichthys, but we must bear in mind 

 that so vast a body needed powerful moving organs and that these iu 

 turn must have had a heavy framework to carry them. The shoulder 

 girdle need not have corresponded in lightness with the cranium. 



■ Dr. Newberry says of a specimen of an apparent homologous plate 

 in his possession (p. 131). "A strong framework was required for the lo- 

 comotive apparatus of so large a fish and some of the bones of the shoul- 

 der girdle are remarkably large and strong. The coracoid for example 

 is nearly two feet in length and one end is a massive, cylindrical bone 

 nearly as large as one's arm. The clavicles are more than two feet in 

 length but were composed of a relatively thin shell of bone which was 

 once lined and. reenforced with cartilage." 



The specimen in the hands of Dr. Newberry if homologous must 

 have differed considerably from that here described, but the differences 

 may have been due to age, sex or species so that it does not necessarily 

 exclude either from the genus. 



We may add that these probably belong to the right side of the fish 

 and the specimen of Dr. N. to the left. The latter also seems to repre- 

 sent only the first of the three bones here described. 



