790 E. T. NEWTON ON SATTItOCEPBALrJS". 



foramina, one to each alveolus. The teeth of the lower jaw close 

 within those of the upper. Intermaxillary very distinct, and united 

 by squamous suture with the maxilla. The alveoli show that the 

 teeth projected. The maxilla has distinct alveoli for teeth, and just 

 within the border on the inner surface there is a regular series of 

 foramina similar to those of the dentary. The exterior of this bone, 

 where not broken, presents a shagreened appearance. The teeth in 

 both jaws are similar, and placed close together in a single row ; 

 those of the lower jaw, however, are rather more compressed than 

 those of the upper, and the anterior teeth of the lower jaw are 

 smaller than the posterior ones. The crowns are enamelled, smooth, 

 lanciform, slightly incurved, and the hinder ones of the lower jaw 

 slightly curved forwards. Their roots are hollow, and slightly 

 grooved on their inner and outer faces. There appear to have been 

 9 or 10 teeth in the intermaxillary, and about 30 in the maxilla ; 

 the number in the dentary not known." Dr. Leidy says there were 

 about 42 teeth in the dentary of this specimen. 



Dr. Hays proposed to place this species in the same genus with S. 

 lanciformis, with the generic name of Saurodon, and the distinctive 

 characters of the genus have been given above (p. 786). The two 

 species are thus distinguished : — 



" 1. S. lanciformis. A groove along the inner surface of the 

 dental bone for the accommodation of the inferior maxillary nerve ; 

 teeth very obtusely lanciform." 



" 2. S. Leanus. Teeth acutely lanciform, much smaller than in 

 preceding species, slightly curved." 



Dr. Harlan in 1834 (Edin. Kew Phil. Journ. vol. xviii. p. 28) 

 pointed out that Dr. Hays was altogether wrong in establishing 

 a new genus (Saurodon) for those two species, when he (Dr. Harlan) 

 had already in 1824 given the name of Saurocephalus. The latter 

 name no doubt has the priority, and must therefore be adopted. 



Prof. Agassiz, in his ' Poissons Possiles ' (vol. v. p. 102), refers 

 certain peculiar teeth from the Chalk of Lewes to the Saurodon Leanus 

 of Hays, bub unfortunately does not give his reason for so referring 

 them. In his description he says, " in place of being regularly 

 conical, as in Saurocephalus, they are curved backward, and their 

 points are cut obliquely with an inflated margin (un rebord renfle). 

 The surface is finely striated from the base almost to the summit. 

 At the base of the tooth is a pronounced annular enlargement, under 

 which one can see the root, which is reticulated. . . . One of these 

 teeth is represented enlarged in fig. 31. The root appears to be united 

 with the bone of the jaw, but it is not sufficiently preserved in 

 our specimen to allow its intimate structure to be made out." 



Why this peculiarly barhed tooth should have been referred to the 

 Saurodon Leanus, in which the crowns of the teeth are simply 

 flattened and slightly incurved, I cannot clearly understand ; for the 

 forms of the two teeth seem to me widely different. Compare 

 Poiss. Poss. t. v. pl.xxv c . f. 30, 31, with Trans. Am. Phil. Soc. 

 1830, vol. iii. pi. xvi. f. 7-9. 



In Dixon's ' Eossils of Sussex ' a specimen is figured (pi. xxxii*. 



