E. T. NEWTON ON SAT7KOCEPHALTJS. 793 



one of the most marked characters given by Drs. Harlan and Hays 

 for this genus. I have examined the type specimen, now in the 

 British Museum, upon which Agassiz founded this species, and also 

 others in the Museum of Practical Geology, and can find no trace of 

 the characteristic foramina: the specimens, it it true, are mere 

 fragments, with one side in the matrix, and therefore one cannot 

 speak with certainty ; but a close examination reveals another most 

 unexpected fact, which is, that the teeth are not implanted in sockets, 

 as in "both upper and lower jaws of Saurocephalus, but are merely 

 ankylosed to the edge of the jaw, having no true fangs. This dif- 

 ference of structure is one of such importance that it cannot hut he 

 regarded as generically distinctive ; and this species must therefore 

 he removed from the genus Saurocephalus. Dr. Leidy, not knowing 

 the mode in which the teeth were fixed to the jaw, referred this 

 species to his genus Protosphyrcena : hut it will be obvious from what 

 has been said above that it cannot be placed in that genus. The 

 only specimens which can be referred to this species are such small 

 fragments that it seems to me impossible to speak with any thing 

 like certainty of their generic affinities ; but their mode of dentition, 

 it will be noticed, agrees with that observed in Cimolichthys levesien- 

 sis — that is, the teeth are ankylosed to the surface of the jaw and 

 are not implanted in sockets ; and I should propose, therefore, pro- 

 visionally to call this species Cimolichthys? striatus, although it 

 seems very probable that it will eventually prove to belong to a 

 distinct genus. 



There is considerable doubt in my mind as to whether the speci- 

 men figured by Dixon as S. striatus (pi. xxxv. fig. 5) really belongs 

 to this species. The teeth certainly appear to be without fangs, and 

 are ankylosed to the jaw in the same manner as they are in C. stria- 

 tus; but the teeth are not so much flattened, neither are they set 

 close together in a regular series, but are placed at intervals ; more- 

 over they are of very different sizes, some being very small. Judging 

 from specimens in the British Museum, it seems likely that the spe- 

 cimen figured by Agassiz is a portion of a maxilla, and may well have 

 belonged to a fish with a lower jaw such as that figured by Dixon 

 (pi. xxxv. fig. 5). The form of this jaw, however, and the mode 

 of its dentition are similar to what are found in Cimolichthys leve- 

 siensis, Leidy, although the forms of the teeth are different ; and, it 

 will be remembered, the form of the maxilla of the latter species is 

 not known. I would suggest, therefore, that until we have better 

 evidence of the form and structure of Agassiz's C. striatus, the jaw 

 figured by Dixon be regarded as the same species, and that both, 

 for the present, be placed in the genus Cimolichthys. 



