786 E. T. NEWTON ON SAUKOCEPBALTTS. 



45. Remakes on Saukocepbaltts, and on the Species ivliich have been 

 referred to that Genus. By E. T. Newton, Esq., E.G.S., H.M. 

 Geological Survey. (Read June 20, 1878.) 



In the year 1824 Dr. Harlan described a portion of a fossil jaw 

 which had been obtained in 1804, during an expedition up the 

 Missouri, from what were believed to be Secondary rocks (Jo urn. 

 Acad. Nat. Sci. Philad. 1830, vol. iii. p. 331). Dr. Harlan thought 

 this specimen showed reptilian affinities, and compared it with 

 certain species of Ichthyosaurus ; but, believing it to be generically 

 distinct, he named it Saurocephalus lanciformis. Prof. Owen sub- 

 sequently showed (' Odontography,' p. 130, pi. 55) that this spe- 

 cimen was to be referred to the group of Eishes. 



There has been so much misunderstanding about the genus Sau- 

 rocephalus, to which certain specimens in this country have been 

 erroneously referred, that it has been thought desirable to bring 

 together all the known facts, in order, if possible, to correct the 

 synonymy of the species. 



Dr. Harlan (I. c. p. 335), after giving the measurements of the 

 bone above mentioned (now known to be a maxilla), says : — " There 

 are eighteen teeth in different states of preservation; the longest 

 are seven tenths of an inch, two tenths only projecting above 

 the bone, the projecting part enamelled, smooth, and shining, Ian- 

 ciform ; the edges are very sharp. . . . The bodies of the teeth 

 are all hollow, and are firmly fixed in a longitudinal groove, there 

 being no distinct separate alveolae. The bodies of the teeth are in 

 close contact throughout. . . . The body of the bone is not per- 

 forated by a canal for the inferior maxillary nerve, in place of 

 which is observed a groove running the whole length of the dental 

 bone, immediately beneath the alveolar portion, on the mesial aspect 

 of the bone ; the bottom of this groove is perforated with foramina 

 for the distribution of the nerves and blood-vessels, equal in number 

 to the teeth (i. e. 18)." 



As regards the teeth being in grooves, Dr. Harlan seems to have 

 been mistaken. Dr. Hays in 1830 (Trans. Am. Phil. Soc. vol. iii. 

 p. 471), when describing his Saurodon Leanus, examined the original 

 specimen of Saurocephalus, and found that the teeth were really 

 lodged in distinct alveoli ; he gives a figure of a portion of the jaw 

 from which the outer lamina has been removed, so as to show the 

 alveoli and the form of the teeth. The close affinity of Sauro- 

 cephalus and Saurodon was recognized by Dr. Hays, and he proposed 

 to place them both in his genus Saurodon, which he thus charac- 

 terized : — " Teeth of lower jaw closing within those of the upper 

 like incisors ; a regular series of foramina along the inner aspect of 

 the jaws near their alveolar margins, for the passage of nerves and 

 blood-vessels to the teeth." 



Prof. Agassiz in the year 1843 (Poiss. Eoss. torn. v. p. 101) referred 



