GEOLOGICAL SURVEY OF THE TERRITORIES. 415 



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 Sphyramidce, those presented by the vertebra? indicating 

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

 of any acanthopterygian fish, and with the complex segmentation 

 of some of the radii approaches nearer such types as the Characinidce. 

 The form of the vertebral centra is utterly different from that of the 

 Sphyrcenidce ; in the Saurodontidce they are short, little contracted 

 medially, and deeply grooved on the sides ; in the Sphyramidce, excep- 

 tional among teleosts in being elongate, much contracted, smooth, and 

 grooveless ! 



The characters presented by the teeth and vertebra? of Saurocephalus 

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

 respects widely removed from that group. On the characters above 

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

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

 that it is related to the Salmonidce, and clupeidce. 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, subcylin- 

 dric, and slightly curved near the apex. In Ichthyodectes the teeth are 

 similar to those of Saurodon, but the margins of both jaws are without 

 the large foramina so prominent- in both the other genera. There 

 appear to be some important differences also in the vertebra?, which 

 will be mentioned below. 



In the Transactions of the American Philosophical Society for 1856, 

 Dr. Leidy treats Saurocephalus as a sphyrsenoid fish, and regards Sau- 

 rodon as a synonyme. He corrects the erroneous references of some 

 European authors, showing the Saurocephalus of Dixon to be a Xiphias, 

 and the Saurodon of Agassiz to be some other genus which he calls 

 Cimolichthys, without characterizing it. This form is supposed to be 

 established on palatine teeth, and if so, is well distinguished, as it will 

 be seen below that Saurocephalus has no teeth on the palatine bones. 

 He also refers two other species of supposed Saurocephalus of Agassiz 

 to a new genus called Protosphyrcena, without characters. This I think 

 rests on mandibular teeth of true Saurocephali. 



SAUROCEPHALUS, (HARLAN.) 



( Journ. Acad. Nat. Sci., Phila., Ill, 337. ? Xiphactinus, Leidy, Proc. Ac. Nat. Sci., Pliila., 



1870, 12.) 



SAUROCEPHALUS LANCIFORMIS, (HARLAN,) 1. C. 



(Med. and Phys. Researches, 362. Leidy, Trans. Amer. Philos. Soc, 1856, Tab. Sauro- 

 don lanciformis, Hays, Trans. Amer. Philos. Soc, 1830, 476.) 



Established on a right superior maxillary bone from a locality near 

 the Missouri Eiver. It differs from that of the other species in having 

 a very elongate superior suture with the premaxillary bone, and in the 

 very short dental crowns, which are as wide as deep. The largest 

 species j known from the jaw. 



