256 W. Davies — On Saurocephahis. 



have no hesitation in stating, that the isolated teeth, portions of Jaws 

 and rostral bones do appertain to the same species of fish. The 

 enamel coating of the crown, and the form and structure of the 

 rostral teeth, are the same in character as the teeth in the maxilla 

 and mandible ; each has a well-developed, laterally compressed 

 crown, with long fangs, adapted for insertion in distinct sockets ; 

 and, moreover, the well-ossified and somewhat massive bones of the 

 mandible correspond in structure, external ornamentation, and even 

 in condition of preservation, with the same elements of the ros- 

 trum. This conclusion is also supported by the fact that wherever 

 the isolated teeth are found, there are also found portions, more 

 or less perfect, of rostra. Associated in the same deposits are 

 frequently obtained coalesced caudal vertebrse similar to, but less 

 symmetrical, and also shorter, higher and thicker, than the con- 

 solidated caudal vertebra3 of the Tetrapterus These vertebrae I 

 have long regarded as belonging to the Saurocephalus lanciformis, 

 as hitherto understood, and have so named them in the National 

 Collection. It was a simple deduction, derived from the fact that 

 a fish armed with such a powerful weapon of offence would have 

 had, to render that weapon effective, an equally powerful organ 

 of propulsion through its native element. And such coalesced 

 vertebrae we find in the tail of XipMas and other recent fishes. In 

 the same deposits frequently occur either singly, or in displaced 

 groups, some long bony and unarticulated fin-rays, which probably 

 appertain to the same species. 



That the teeth, in form and mode of implantation in distinct sockets, 

 simulate the teeth of a Sphyrgenoid fish, is apparent, but no fishes of 

 this family have the premaxillaries consolidated and prolonged into 

 a bony rostrum ; neither have any of the long-beaked fishes of the 

 Scomber-Esocidas, in which family these remains have latterly been 

 classed. Again, the pair of backward-pointing teeth of the rostrum, 

 with the well-developed armature of the maxillaries and dentary 

 bones, and also the abrupt termination of the mandibular symphysis, 

 armed with three strong teeth on either side, two of which are 

 horizontally directed; preclude these remains from association with 

 XipMas, in which genus the jaws are all but edentulous, and the 

 mandibular symphysis acutely pointed. 



Therefore, neither of the generic names proposed by Prof. Leidy 

 are applicable to these remains, but having included in ProtosphyrcBna 

 two species that are generically distinct, viz. the species under con- 

 sideration, and the Saurocephalus striatus, founded by Agassiz upon 

 mere fragments of two jaws, having respectively five and three 

 teeth in situ ; and these, not being inserted in sockets, are clearly not 

 referable to Saurocephalus, therefore Leidy's genus might be re- 

 tained, provisionally, for the S. striatus of Agassiz. It is thus 

 evident that the British fossils hitherto referred to Saurocephalus 

 lanciformis are types of a new genus. 



Prof. Cope, in 1872, founded his genus Erisichthe upon some 

 remains found in a Cretaceous deposit in Kansas ; these he sub- 

 sequently figured in his larger work on the " Cretaceous Vertebrata 



