go NEW YORK STATE MUSEUM 



maxillary arch was not developed. Another feature which influenced the 

 novel association of Arthrodires with Dipnoans was the parallelism, pre- 

 viously noted by Newberry,' between the dentition of Dinichthys and that 

 of Protopterus. The absence of any indication of a hyomandibular bone, 

 even in the most admirably preserved specimens, and of more than a single 

 ossification in the lower jaw, were considered sufficient reasons for excluding 

 Arthrodires from Teleostomes. 



This provisional classification of Arthrodires with Dipnoans met with an 

 indifferent reception on the part ot most paleontologists, and was afterwards 

 rejected by some of its early supporters, notably Traquair and Bashford 

 Dean. It was even conceded by Smith Woodward himself a few years 

 later, that " the systematic position of this extinct order is indeed doubtful."^ 

 Traquair's defection dates from 1900, when he declared, in his Bradford 

 address,^ in favor of considering Arthrodires as " Teleostomi belonging to 

 the next higher order, Actinopterygii." The following year Dean expressed 

 the radical view that they were not fishes at all, but representatives of a 

 distinct class, called by him Arthrognathi, and conceived to have possible 

 kinship with Ostracophori.'* It was even allowed that subsequent researches 

 might demonstrate a union between Arthrognaths and Ostracophores, 

 whereby the time-honored group of Placodermata would be restored. This 

 last was a complete reversal of his former view that the " jaws, specialized 

 dentition, fin spines, and highly evolved pelvic fins at once separate this 

 group [Arthrodira] from the lowly Ostracoderms." ^ 



By far the most amplitudinous extension of the term Placodermata is 

 that proposed by Otto Jaekel, in 1902, whereby the Pteraspids, Trematas- 

 pids, Cephalaspids, Asterolepids and Coccosteans were all embraced within 



' Newberry, J. S. O. Geol. Sur. Rep't Pal. 1875. 2: 15. The suggestion is here 

 advanced that Protopterus and Lepidosiren are lineal descendants of '' Placoderms." 



^Woodward, A. S. Outlines of Vertebrate Palaeontology. 1898. p. 64. 

 3 Traquair, R. H. Vice Presidential Address. Brit. Ass'n Adv. Sci. Bradford meet- 

 ing, Rep't. 1900. p. 779. 



■•Dean, B. Palaeontological Notes. New York Acad. Sci. Mem. 1901. 2:113. 

 ijdem. Fishes, Living and Fossil, N. Y. 1895. p. 130. 



