g2 NEW YORK STATE MUSEUM 



dentition. But this autostylism has yet to be verified, and, if proved, the 

 possibility that it may be a secondary feature, associated with the evolution 

 of a peculiar dentition, must not be forgotten. Much more may be said for 

 their claim to be regarded as a highly specialized race of primitive Teleo- 

 stomi. Besides a well developed lower jaw, bones comparable to the ele- 

 ments of a secondary upper jaw are known, and in a general way the 

 disposition of the cranial roofing bones, and the arrangement of the endo- 

 skeletal elements of the pelvic fins, tend to conform to the normal Teleo- 

 stome type. In fact, Dr Traquair has expressed the opinion that the 

 Arthrodira are Teleostomi and Actinopterygii.' 



in his description of some Dinichthyid remains from Ohio, published 

 in 1905, Mr L. Hussakof =• refers to them as " Placoderms," apparently using 

 the term in its familiar acceptance. Their position is also left undetermined 

 by E. Ray Lankester, in his interesting lectures on Extinct Animals, 

 recently published in book form.^ Dr Lucas's popular treatise on Animals 

 before Man in North America places them in association with lung fishes, 

 in accordance with Smith Woodward's idea. One other popular handbook 

 claims attention, not only because it is an extremely useful work covering 

 the whole subject of fishes, but because of the author's extensive acquaint- 

 ance with fossil as well as recent forms. We refer to President Jordan's 

 Guide to the Study of Fishes [N. Y. 1905], in the first volume of which, at 

 page 582, the relations of Arthrodires are discussed in following wise : 



These monstrous creatures have been considered by Woodward and 

 others as mailed Dipnoans, but their singular jaws are quite unlike those of 

 the Dipneusti, and very remote from any structures seen in the ordinary 

 fish. The turtlelike mandibles seem to be formed of dermal elements, in 

 which there lies little homology to the jaws of a fish, and not much more 

 with the jaws of Dipnoan or shark. 



The relations with the Ostracophores are certainly remote, though 

 nothing else seems to be any nearer. They have no affinity with the true 

 Ganoids, to which vaguely limited group many writers have attached them. 



'In his latest reference to this subject, however, he admits that they are of uncertain 

 subclass. Compare, for instance, his description of Coccosteus angustus in Roy. 

 Soc. Edinburgh Trans. 1903. 40: 732. 



^Hussakof, L. Notes on the Devonic "Placoderm," Dinichthys intermedins Newb. 

 Am. Mus. Nat. Hist. Bull. 1905. 2i: 27-36. Also, more recently. Studies on the Arthro- 

 dira, in the memoirs of the same institution. 1906. g: 105-54. 



3 Lankester, E. R. Extinct Animals. N. Y. 1905. p. 256. 



