PORTHEUS. 101 



Kansas. The teeth bear much superficial resemblance to those of Protosphyrsena 



Fig. 28. Portheus molossus, Cope ; pelvic fin, about one fifth nat. size. — Upper Cretaceous (Niobrara Group) ; 



Kansas, U.S.A. B. M. no. P. 6326. 



and of Pterodactyles, but they are distinguished by their large pulp-cavity and 

 splintery fracture. 



1. Portheus mantelli, Newton. Plate XXI, figs. 8, 9 ; Text-figure 29. 



1822. "Unknown fish," G. A. Mantell, Foss. South Downs, p. 241, pi. xlii, figs. 1, 3, 4. 



1835. Megalodoti sauroides, L. Agassiz, Poiss. Foss., Feuill., p. 55 (name only). 



1836. Megalodon ? lewesiensis, Gr. A. Mantell, Descript. Catal. Geol., etc., Mus. Sussex Sci. Lit. Inst., 

 ed. 5, p. 30. 



1837-44. Hypsodon lewesiensis, L. Agassiz, Poiss. Foss., vol. v, pt. i, p. 100 (in part), pi. xxv a, fig. 



3 ; pi. xxv b, figs. 1-3. 

 1877. Portheus mantelli, E. T. Newton, Quart. Journ. Geol. Soc, vol. xxxiii, p. 510. 

 1901. Portheus mantelli, A. S. Woodward, Catal. Foss. Fishes B. M., pt. iv, p. 95. 



Type. — Imperfect left maxilla and premaxilla from one of the Turonian zones ; 

 British Museum. 



Specific Characters. — Premaxilla with five teeth of unequal size. Maxilla about 

 four times as long as the premaxilla, and its oral border in the form of a slightly 

 concave arch. Teeth smooth, not facetted. 



Description of Specimens. — The type specimen in the Mantell Collection (nos. 

 406G-67) is an upper jaw measuring only 18 cm. in length (PL XXI, fig. 8) ; but 

 another maxilla, sufficiently similar to have belonged to the same species, is 

 larger, and other fragmentary remains suggest that Portheus mantelli attained as 

 large a size as the typical P. molossus, of which the skull sometimes measures 

 45 cm. in length, while the whole fish cannot have been less than 4 — 5 metres in 

 length. Unfortunately, only isolated bones have hitherto been found in the 

 English Chalk. 



The premaxilla (PI. XXI, fig. 8, pmx. ; fig. 8 a) is deeper than wide, and its 



