180 CATALOG OF FOSSIL FISHES IN THE MUSEUM 



angular.^' But the demonstration in recent years that the Crosso- 

 pterygii are ancestral to the Tetrapoda, necessarily changed this point 

 of view, and the Crossopterygian mandible is now regarded as pos- 

 sessing elements homologous with those of primitive amphibia. This 

 conclusion rests on the cumulative work of Smith Woodward, Broom, 

 Williston, Gregory and Watson. Broom^^ in a special paper on the 

 subject, in 1913, showed that in the mandible of the Crossoptery- 

 gian Sauripterus taylori, from the Chemung of Pennsylvania, the 

 infradentaries represent the elements found in the typical Stego- 

 cephalian mandible, for instance, Trimerorachis, and that they may be 

 interpreted as splenial, preangular, angular, surangular, prearticular 

 and articular. So, too, in the latest paper on the subject, by W. K. 

 Gregory,^* this is the view advocated. And it is in line with this 

 newer interpretation that the elements in the mandible of Onycho- 

 dus are named above. Our specimen does not show the front portion 

 of the mandible, so that the splenial, if present in Onychodus, is not 

 shown. And at the posterior end, the surangular is not preserved. 



1. Specimens from the Delaware limestone (Mid. Devonic); 

 Delaware, Ohio. 



E 1871 A series of six premandibular teeth with their supporting 

 symphyseal bone. The teeth are curved, as is usual in 

 these specimens (PI. 58, fig. 2). 



E 1872 A series of symphyseal teeth, and their supporting bone- 

 One tooth shifted from its position. 



This and the following specimen were presented by 

 Mr. E. E. Teller. 



E 1873 Adetached tooth, 4 cm. in height. (PL 58, fig. i) 



2. Specimens from the Onondaga limestone at Leroy, N. Y. 



E 2556 The fine mandible discussed in the preceding pages and 

 illustrated in Plate 58, figures 3, 3a, 3b, and text-fig. 59. 



87 See for instance the excellent figure of the mandible of Rhizodus hibberti in Smith Woodward's 

 Catalog of Fossil Fishes, Part II, pi. xii, fig. i. 



8s Broom, R. : On the structure of the mandible of Stegocephalia Anat. Anz., xlv, 77-78. 



S9 Gregory, W. K.: Present status of the problem of the origin of the Tetrapoda with special refer- 

 ence to the skull and paired limbs. Annals N. Y. Acad. Set., xxvi, 317-383, pl- iv, igis- See especi- 

 ally P- 334 for table of homologies between bones of mandible in Rhipidistia and Stegocephah, and for 

 references to the work of Smith Woodward, Williston, Broom, and Watson, on which these conclusions 

 rest. 



