788 E. T. NEWTON ON SATTKOCEPHALUS. 



for their reception, Erisichthe, believing that the differences between 

 them and Saurocephalus were of even more than generic importance. 

 The similarity between the portion of lower jaw figured by Cope (I. c. 

 pi. xlviii. f. 6) and that given by Dixon (pi. xxxi. f. 12) is such that 

 no one would have much doubt of their generic relationship. Some 

 specimens, obtained during 1877 from the Niobrara Cretaceous of 

 Kansas, have enabled Prof. Cope to make still further additions to 

 our knowledge of these peculiar fishes (Bulletin 6, Geol. Surv. Terr. 

 1877, p. 821) ; and he describes three new species, which he distin- 

 guishes by the form of the rostrum, and then concludes by saying, 

 " A fourth species has been found in England, and figured by Dixon 

 in the ' Geology of Sussex/ The portions represented in this work 

 [Dixon] are the mandibles, which resemble those of the E. nitida, 

 and which were supposed at that time to belong to a species of 

 Saurocephalus. A muzzle, perhaps of the same species, was re- 

 garded as a Sword-fish, which was called Xiphias Dicconi by 

 Agassiz. It should be now termed Erisichthe Dixoni." Prof. Cope 

 does not appear to have known that Dr. Leidy had already named 

 the English specimen Protosphyrcena ferox, by whom also the name 

 of Xiphias Dixoni was proposed for the rostrum figured by Dixon. 

 Agassiz was not the author of this name. 



A due consideration of the facts of the case show conclusively, as 

 it seems to me, 1st, that the specimens figured by Messrs. Agassiz 

 and Dixon, and referred by them to the Saurocephalus lanciformis 

 of Harlan, do not belong to that genus and species, and this species 

 will have to be expunged from our lists of British fossils ; 2nd, that 

 these specimens do agree generically with those described and 

 figured by Prof. Cope. 



Dr. Leidy in 1856 proposed, as already mentioned, the generic 

 name of Protosphyrcena for these British specimens ; and this name 

 therefore must be adopted, and not that of Erisichthe, which was 

 given by Prof. Cope in 1872 to the American specimens. 



The most important characters of the genus Protosphyrcena, as we 

 now know them, are the elongation of the ethmoidal region into a 

 rostrum resembling that of the sword-fish, and the peculiar form of 

 the mandible (vide Dixon, Eoss. Suss.). Both the upper and lower 

 jaws have large compressed teeth, lodged in distinct alveoli, besides 

 other smaller teeth. The following description of the Protosphyrcena 

 (Erisichthe) nitida, Cope, recently obtained from the Niobrara 

 Cretaceous of Kansas, will give the best idea of the structure of the 

 head of these fishes (Cope, Bull. Geol. Surv. Terr. 1877, vol. iii. n. 4, 

 p. 821) : — " Erom this and other specimens I discover that the 

 anterior portion of the skull, probably the ethmoid bone, is produced 

 into a long beak, in general form similar to the sword-like snout of 

 the Sword-fishes of modern seas. ... A remarkable feature of the 

 genus is displayed in the mandibles. Each of these is compound in 

 the region usually composed of the simple dentary bone. It there 

 consists of three parallel elements, an internal and an external 

 embracing a median element. The inner bears a band of teeth en 

 brosse on its inner and superior aspect, and the external a few teeth 



