E. T. NEWTON ON SAUKOCEPHALT7S. 789 



of similar character on its superior edge. The large lancet-shaped 

 teeth are borne by the middle element, excepting some of the largest 

 near the symphysis. Two of these on the inner side of the ramus 

 originate in the internal bone. The maxillary bone forms the 

 greater part of the arcade of the mouth, and has no superior articu- 

 lation with the facial part of the skull. It is attached by a simple 

 sutural articulation with the prem axillary, so as to permit of some 

 lateral motion. The premaxillary also has no superior condyle 

 articulating with the cranium, but the entire length of its superior 

 margin is applied in a groove of the ethmoid bone, so as to be im- 

 movable. Anterior to the premaxillary bones, on the inferior aspect 

 of the ? ethmoid, is situated a pair of large, compressed, double- 

 edged teeth, whose alveoli are close together." 



The different forms of the rostra have been taken by Cope as 

 specific characters. In P. nitida " this weapon is distinguished by 

 the flat superior surface of its distal half. The section in this 

 region is semicircular." P. penetrans " has a snout of uniformly 

 oval section at all points." In P. ziphioides " the form of the 

 muzzle is quite peculiar. Its shaft is depressed, with a strongly 

 convex inferior surface and a slightly convex superior surface, the 

 two separated by an obtuse angular border," &c. 



The rostrum figured by Dixon is nearly circular in section 

 throughout, and therefore differs from all the above American 

 species. This difference was observed by Cope, who proposed that 

 this specimen and the mandible represented in the same work 

 should be known as Erisichthe Dioconi ; this name, however, must 

 give place to the older one of Protosphyrcena ferooo, given by Leidy 

 to the mandible in 1856. 



Although numerous specimens of teeth, parts of jaws, and rostra 

 have been obtained from British Cretaceous strata, yet all the frag- 

 ments of rostra with which I am acquainted resemble that figured 

 by Dixon in being nearly circular in section ; the other portions 

 found are not sufficient to afford grounds for specific distinction. 

 At present, therefore, we are only able to record one species of this 

 genus as occurring in Britain, viz. Protosphyrcena ferooo. 



Sir Philip Egerton has kindly called my attention to the following 

 foreign species which have been referred to the genus SaurocepTialus, 

 viz. JS. albensis, Pictet & Campiche ; S. dispar, Hebert ; 8. incequcdis, 

 Minister ; S. infleocus, Pictet & Campiche ; and S. substriatus, Miinster. 

 These species have all been founded on isolated teeth, and it seems 

 to me that there must be considerable doubt as to their generic and 

 specific affinities. 



JSaurodon Leanus was first described by Dr. Hays in 1829 (Trans. 

 Am. Phil. Soc. 1830, vol. iii. p. 471). The specimen was obtained 

 from the Greensand near Moorestown, New Jersey. It includes 

 the upper and lower jaws of both sides. The author recognized 

 the close relation existing between this specimen and the Sauro- 

 cephcdus lanciformis of Harlan, and in his description mentions, 

 among other points of structure, the following :■ — " The dentary has 

 a single row of alveoli, and just below the border there is a row of 



