Nov. 18, 1870.] ^-^-^ . tCope. 



ON THE SAURODONTID^. 

 By Edwakd D. Cope, A. M. 



Bead before the American Philosophical Society, November l^th, 1870. 



The genus Sauroeephalus of Harlan and its allies have been referred 

 to the neighborhood of the Acauthopterygian family of the Sphyrcenidce 

 by Prof. Agassiz in his Poissons Fossiles, after having been regarded by 

 Harlan and Hays as reptilian. Tbis was an important step in the right 

 expression of its affinities ; but I take the present opportunity of making 

 another progress in the true inter^jretation of its relations, favored as I 

 am by the opportunity of examining new material not accessible to former 

 authors. My conclusion, it will be observed, differs widely from that 

 heretofore maintained. 



Some years after Harlan's description of 8aurocephalus lanciformis 

 appeared. Dr. Hays described a second species under the name of Sau- 

 Todon leanus. This I believe to represent a genus distinct from the 

 former. A third genus more remote is characterized in the present 

 article. 



The characters of first importance which may be assigned to these 

 genera are : — 



Vertebrae short, numerous ; their neural arches united with centrum 

 by persistent suture. Tail vertebrated or .heterocercal. Superior arch 

 of the mouth formed by the short premaxillaries and long maxillaries. 

 Teeth one-rowed, with fangs received into alveoli more or less confluent 

 at their openings. Anal or caudal radii "with complex segmentation. 



These characters are most of them entirely contradictory of any affinity 

 to the Sphyrsenidffi, those presented by the vertebrse indicating a nearer 

 approach to Amia. The structure of the mouth is not that of any 

 Acauthopterygian fish, and with the complex segmentation of some of 

 the radii approaches nearer such types as the Characinidse. The form of 

 the vertebral centra is utterly different from that of the Sphyriaenidas : 

 in the Saurodontidas they are short, little contracted medially, and deeply 

 grooved on the sides ; in the Sphyrsenidae, elongate, much contracted, and 

 exceptional among Teleosts in being smooth and grooveless ! 



The characters presented by the teeth and vertebrse of Saurocephalus 

 remind one much of Serrasalmo, though the genus is no doubt in other 

 respects widely removed from that groui). On the charactei's above 

 enumerated, I propose the family Saurodontidse. Its precise position I 

 am not prepared to determine at present, though I have little doubt that 

 Amia is its nearest living ally. With the remains of species of this group 

 occur numerous scales, which may belong to the former. They are 

 cycloid and without ganoine. 



The three genera are distinguished by the form of their jaws and 

 teeth : in Saurocephalus the crowns are shortened, much compressed, 

 and with sharp edges ; in Saurodon the crowns are elongate, subcylindric 

 and slightly curved near the apex. In Ichthyodectes the teeth are similar 



A. p. S. — VOL. XI — 39e. 



