E. T. NEWTON ON SATTROCEPHALUS. 791 



fig. 10) which bears teeth similar to those just mentioned as figured 

 by Agassiz, and, like them, is referred to Saurodon Leanus. This 

 specimen is described in the text as follows : — " The specimen figured 

 is of great interest; it shows the lower jaws united at the symphy- 

 sis, and a portion of the right palatine bone in its natural position. 

 . . . The barbed teeth described by M. Agassiz are those on the 

 palatine bone, their edges are finely serrated ; the teeth of the lower 

 jaw are of an entirely different form, the base is broad and fluted, 

 the blade compressed and recurved, with a sharp, finely serrated 

 edge ; they are separated by wide intervals, which are filled by in- 

 numerable small pointed teeth." 



The differences between this specimen and the type of Saurodon 

 Leanus , Hays, are so obvious that surely they only need to be 

 pointed out in order to be generally acknowledged. Notwithstand- 

 ing this, and although Dr. Leidy first called attention to these differ- 

 ences in the year 1856 (Trans. Am. Phil. Soc. 1860, xi. p. 94), up to 

 the present time the name of Saurodon Leanus has been retained in 

 our lists of British fossil fishes. Dr. Leidy, towards the end of his 

 paper, says : — " To Saurodon Leanus, Hays, Agassiz has erroneously 

 referred the fragment of a palate-bone with teeth (Poiss. Toss. v. 

 p. 102, pi. xxv c . figs. 30, 31) of another large Sphyraenoid fish from the 

 Chalk of Lewes, England. Though the true Saurocejphalus may have 

 had semibarbed teeth to the palate-bone, like those just referred to 

 in the fragment described by Agassiz, yet this could not fairly be 

 inferred from the condition of the living Sphyrcena." 



Dixon has noticed and represented (Geol. Sussex, p. 373, pi. xxx. 

 figs. 28, 29, pi. xxxii*. fig. 10) several large, isolated, semibarbed 

 teeth, and a lower jaw and palate-bone with teeth, which, follow- 

 ing Agassiz, have been referred to Saurodon Leanus, Hays, "to which 

 they certainly cannot belong." Prom the above quotation it will 

 be seen that Leidy is firmly convinced of the generic distinctness of 

 the true Saurodon Leanus and the specimens figured by Agassiz and 

 Dixon and called by the same name. 



In order to be as certain as possible about this matter, I have com- 

 pared the original specimen figured by Agassiz and Dixon, and also 

 another in the Museum of Practical Geology which has similarly 

 barbed teeth, with the descriptions and figures given by Hays and Leidy, 

 and I find that there are even greater differences than have hitherto 

 been pointed out. Agassiz's type is merely a fragment of bone with 

 two or three barbed teeth ; both the other specimens have part of 

 the lower and upper jaws ; but in neither of them does there appear 

 to be any trace of the maxilla or premaxilla. The lower jaw is 

 shallow in proportion to its length, and has as great an extent hori- 

 zontally as vertically ; in S. Leanus, Hays, on the contrary, the 

 lower jaw has a greater vertical than horizontal extent. In the 

 British specimens the large teeth in the lower jaw have compressed 

 crowns, curved backwards and striated ; but these have no roots lodged 

 in sockets, the expanded base resting upon, and being firmly anky- 

 losed to, the jaw. The form of the mandible might have led one to 



