104 



FOSSIL FISHES OF THE ENGLISH CHALK. 



small toothless presymphysial bone in the mandible. Vertebrae as in Ichthyodectes 

 and Porth&us. 



Type Species. — Saurodon leanus (Hays, Trans. Amer. Phil. Soc., n. s., vol. iii, 

 1830, p. 476, pi. xvi), from the Upper Cretaceous of New Jersey, U.S.A. 



Remarks. — This genus is best known by nearly complete skulls and other 



Fig. 31. Saurodon xiphirostris, Stewart; left side-view of crushed head, with mandible displaced 

 forwards, about one half nat. size. — Upper Cretaceous (Niobrara Group) ; Kansas, U.S.A. ag., 

 articulo-angular ; d., dentary; eth., mesethmoid ; fr., frontal; mi., maxilla ; pmx., premaxilla; 

 ps., presymphysial bone ; pto., pterotic (including squamosal). After Alban Stewart. 



remains from the Upper Cretaceous (Niobrara Group) of Kansas, U.S.A. The 

 remarkable presymphysial bone has been found in several specimens, forming 

 a triangular, toothless, and pointed projection in front of the mandible 

 (Text-fig. 31, ps.). 



1. Saurodon intermedius (Newton). Text-figure 32. 



1878. Baptinus intermedins, E. T. Newton, Quart. Journ. Geol. Soc, vol. xxxiv, p. 440, pi. xix. 

 1890. Saurocejrfialus intermedius, Woodward and Sherborn, Catal. Brit. Foss. Vertebrata, p. 181. 

 1901. Saurodon intermedius, A. S. Woodward, Catal. Foss. Fishes B. M., pt. iv, p. 112. 



Type. — Head, etc., probably from zone of Schloenbachia v avians ; British 

 Museum. 



Specific Characters. — Teeth much longer and less compressed than in the type 

 species ; only five dental alveoli in the premaxilla and about thirty-two in the 

 maxilla. Maximum depth of maxilla contained about two and a half times in its 

 length ; maximum depth of mandible slightly less than one quarter of its length. 

 Bones Avithout external ornamentation. 



Description of Specimen. — In the type specimen (Text-fig. 32), which still 

 remains unique, the upper jaw measures about 10 cm. in length. So far as it can 

 be compared, the head agrees very closely with that of the species of Saurodon 



