100 



FOSSIL FISHES OF THE ENGLISH CHALK. 



described from the Cretaceous of Istria in 1850. 1 Portheus may, in fact, be merely 

 ;i synonym of Ohiroccnfrifrs. 



Fig. 26. Portheus molossus, Cope ; head with opercular apparatus, about one quarter nat. size. — Upper 

 Cretaceous (Niobrara Group); Kansas, U.S.A. ag., articulo-angular ; co., cireumorbital cheek- 

 plates ; d., dentary ; epo., epiotic ; eth., mesethmoid ; fr., frontal; mx., maxilla; op., operculum; 

 pi., palatine ; pmx., premaxilla ; pop., preoperculum ; prf., prefrontal ; ptf., postfrontal ; pto., pterotic 

 (including squamosal); qu., quadrate; scl., ossified sclerotic; socc, supraoccipital ; v., anterior 

 vertebra;. After Alban Stewart. 



Fio. 27. Portheus molossus, Cope ; right pectoral fin, about one fiftb nat. size. — Upper Cretaceous 

 (Niobrara Group) ; Kansas, U.S.A. After H. P. Osborn. 



The general characters of the head and paired fins of Portheus are shown in the 



accompanying Text-figs. 2G — 28, which represent parts of the type species from 



1 J J. Heckel, "Beitragezur Kenntuiss der Fossilen Fische Oesterreichs," Denkschr. k. Akad. 

 Wiss , math.-naturw. CI., vol. i, 1850, p. 203, pis. xiii— xv. 



