PORTHBITS. 



99 



Genus PORTHEUS, Cope. 



Megalodon, L. Agassiz (non Sowerby, 1829), Poiss. Foss., Feuill., 1835, p. 55 (in part). 

 Hijpsodon, L. Agassiz, loc. cit., 1837, p. 104 (in part). 

 Xiphactinus, J. Leidy, Proc. Acad. Nat. Sci. Philad., 1870, p. 12. 

 Portheus, E. D. Cope, Proc. Amer: Phil. Soc, vol. xii, 1872, p. 331. 



Generic Characters. — As Tchthyodectes, but teeth irregular in size. 



Type Species. — Portheus molossus (Cope, Proc. Amer. Phil. Soc, vol. xii, 1872, 

 pp. 175, 333, and Vert. Cret. Form. West, 1875, pp. 184, 194, fig. 8, pis. xxxix— 

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



Remarks. — The remains of this genus were first discovered in the English 

 Chalk, and were originally named Megalodon and Hypsodon by Agassiz without 

 description or definition. The jaws were subsequently figured by the same author 

 under the indefinite name Hypsodon leivesiensis, which now proves to have been 

 given to remains of two distinct genera (see also Pachyrhizodus, p. 124). Similar, 

 but more satisfactorily preserved, fossils were afterwards found in the Chalk of 

 Kansas, and the genus to which they belong was first defined by Cope in 1872 

 under the name of Portheus. A fin-ray, doubtless of the same fish but insufficient 

 for generic definition, was also described from the Chalk of Kansas by Leidy, who 

 named it Xiphactinus audax. Later discoveries in the Chalk of Kansas 1 have made 



/////» viz / 



py 



Fig. 25. Chirocentrites coroninii, Hockel ; fish, nearly one quarter nat. size. — Neocomian ■ Istria 



After J. J. Heckel. 



known the whole skeleton except the dorsal and anal fins, of which it can only be 

 stated that they were remote and opposite. The discovery of these fins is an 

 important desideratum, because in all other features Portheus agrees very closely 

 with Chirocentrites (Text -fig. 25), of which nearly complete skeletons were 



1 See especially A. E. Crook, "Ueber einige fossile Knochenfische aus der mittleren Kreide von 

 Kansas," Paheontogr., vol. xxxix, 1892, pp. 114-122, pi. xviii; O. P. Hay, "Observations on the 

 Genus of Fossil Fishes called by Professor Cope Portheus, by Dr. Leidy Xiphactinus; 1 Zool. Bull., 

 vol. ii, 1898, pp. 25—54, figs. 1—16; A. Stewart, "Teleosts of the Upper Cretaceous," Univ. Geol. 

 Surv. Kansas, vol. vi, Paleont., pt. ii, 1900, pp. 265—295, pis. xxxiii— xlviii ; H. F. Osborn, "The 

 Great Cretaceous Fish Portheus molossus, Cope," Bull. Amer. Mus. Nat. Hist., vol. xx, 1904 pp 

 377—381, pi. x. 



