^60 TF. Dav/es — On Saurocephalm. 



remains which have hitherto borne the name will henceforth appear 

 in the corrected lists thus : 



Erisichthe Bixoni, Cope fsine descrip.); Bull, of the U.S. Geol. and Geog. Surv., 



vol. iii. 1877, p. 821. 

 Saurocephalus lanciformis. Had. ; Agassiz, Eech. Poiss. Foss., torn. v. pt. 1, p. 



102, pi. 25c. figs. 21-29. Dixon, Geol. Suss., 1850, p. 374, pi. 30, figs. 



21, 21a-d. pi. 31, fig. 12, pi. 32*, fig. 1, pi. 34, fig. 11. 

 Protosphyrcena ferox, Leidy, in part (sine descrip.) ; Trans. Amer. Phil. Soc, 



1857, vol. xi. p. 13. 

 Xiphias Dixoni, Leidy, in part (sine descrip.), op. cit. 



All the European species referred to Saurocephalus by continental 

 authors having been founded upon isolated teeth, similar in character 

 to those erroneously referred to the genus by Agassiz, will have to 

 be transferred to Erisiclitlie or some allied fishes. Nevertheless, 

 there is evidence that Saurocephalus is a European genus; for among 

 the fossil fishes from the Upper Cretaceous beds of Maestricht, in the 

 Van Breda collection in the British Museum, are remains of an un- 

 described species. They are contained in a split block of the well- 

 known friable matrix, which expose on their opposing surfaces the 

 greater portion of a ramus' of a mandible with teeth. Since its 

 acquisition by the British Museum, a maxillary and some bones of 

 the head which were present in the matrix have been developed, 

 but unfortunately the bones are in too fragmentary a condition to 

 be satisfactorily determined. The maxilla is also imperfect, and is 

 so placed that the form and dimensions of so much as is preserved 

 cannot be ascertained, for the anterior end underlies the dentary 

 bone, at right angles and in immediate contact with it ; the upper 

 sutural margin also, if present, is imbedded in the matrix among 

 the crushed bones of the head, but fortunately, as regards the satis- 

 factory determination of the genus, it shows the inner and most 

 important view. The length of the alveolar border as seen is 2^ 

 inches, and the greatest vertical depth of the bone exposed is 7 

 lines. It contains twenty teeth, the crowns of some are broken, but 

 those of the first eight are entire, and some are represented by the 

 apices of successional teeth just emerging above the margins of their 

 respective alveoli. The teeth are closely set, having comparatively 

 short depressed crowns with long bases. The inner side of the 

 alveolar border is slightly depressed to a vertical depth of about one 

 line ; about midway along this depression, and opposite to the 

 vertical axis of the teeth, commences a series of short oblique notches, 

 which terminate in foramina upon the raised portion of the bone. 

 These foramina are, according to Leidy, characteristic of the genus, 

 their function being the nutrition of the successional teeth. It 

 differs from the maxillaries figured by the same author in being 

 intermediate in size between Suurocephalus lanciformis and ;S'. 

 Leanus; the apices of the teeth are also longer in proportion to their 

 breadth than in S. lanciformis, and this last species does not appear 

 to have any foramina! notches ; those in S. Leanus are straight, and 

 have their origin at the alveolar margin ; whilst in our specimen 

 they are oblique, and commence about midway from the margin. 

 In splitting the block the dentary bone was unfortunately divided, 



