E. T. NEWTON ON SAUROCEPHALUS. 787 



certain large flattened teeth from the White Chalk of Sussex, which 

 had been figured by Dr. Mantell in his ' Geology of Sussex ' (pi. xxxiii. 

 figs. 7 & 9), to Harlan's Saurocephalus lanciformis, but does not 

 state why he so refers them. A comparison of Agassiz's figures 

 (pi. xxv c . f. 21-29) with those given by Harlan (Z. c. pi. xii.) will, 

 I think, be sufficient to throw doubt upon their belonging to the 

 same species. Prof. Agassiz doubtless had good reasons for referring 

 these teeth to Harlan's genus and species, but does not mention 

 them in the text. If Agassiz's figures be compared with figure 7 of 

 Harlan's plate, the close resemblance between them will be at once 

 seen ; and when first referring to this plate I was struck with the 

 similarity, and thought that the well-known teeth from the English 

 Chalk had been correctly referred to Harlan's species ; but upon 

 turning to the explanation of the plate I found that this identical 

 tooth (fig. 7) was circular in section, and, moreover, that it belonged 

 to an Ichthyosaurus which was described in another paper, but the 

 figures had been mixed on this plate. Is it possible that, in some 

 way, this unfortunate intermingling of the figures was the cause of 

 a mistake ? 



Dixon, in his 'Fossils of Sussex' (1850), figured a lower jaw 

 (pi. xxxi. f. 12) bearing large flattened teeth, resembling those figured 

 by Agassiz. This jaw he also refers to Saurocephalus lanciformis. 

 In a note on page 375 he says that " Sir P. Egerton has obtained a 

 specimen of Saurocephalus lanciformis showing that the premaxillary 

 bones were prolonged into a rostrum, as in the Xiphioids (tab. 

 xxxii*. fig. 1)". 



In the year 1856 Dr. Leidy carefully redescribed the original 

 specimen of Saurocephalus lanciformis (Trans. Am. Phil. Soc. 1860, 

 vol. xi. p. 91, pi. vi.) ? and pointed out, among other interesting cha- 

 racters of the specimen, that the teeth " have the same mode of 

 insertion and order of succession as in the existing Sphyrcena,^ 

 and that their crowns have the " trenchant borders finely denti- 

 culate." Dr. Leidy considers that the isolated teeth figured by 

 Agassiz (I. c. pi. xxv c . f. 21-29), and the jaws and teeth figured by 

 Dixon (I. c. pi. xxx. f. 21, pi. xxxi. f. 12, pi. xxxiv. f. 11), have 

 been erroneously referred to Saurocephalus lanciformis, and therefore 

 establishes a new genus and species for their reception, which he 

 names Protosphyrcena ferox. The rostrum figured by Dixon (pi. 

 xxxii*. f. 1) he did not think belonged to the same fish, and conse- 

 quently gave it another name, Xiphias Dixoni. 



The specimens lately obtained in America by Prof. Cope show that 

 Sir Philip Egerton was correct, and that this rostrum and lower jaw 

 do belong to the same kind of fish. 



A corrected list of the fishes which have been attributed to 

 Saurocephalus is given at the end of Dr. Leidy's paper. This list, 

 with some modifications, is included in the one given below (p. 794). 



More recently specimens of jaws with teeth, resembling those 

 represented by Dixon, have been discovered in the Cretaceous rocks 

 of North America, and described by Cope (Geol. Surv. Terr. 1875, 

 vol. ii. Cret. Vert. pp. 217, 275), who has established a new genus 



3g2 



