Mr. A. S. Woodward ow Rhaphiosaurus. 351 



The fossil in question was discovered by Mr. James Carter, 

 F.R.C.S., and ])resented by him to the Woodwardian Museum, 

 Cambridge ; and, through the kindness of Prof. Hughes, tlie 

 present writer has lately had the privilege of examining and 

 comparing the specimen with fossils in the British Museum. 

 As a result of the study it may be definitely asserted that 

 ^' RhapJiiosaurus " is founded upon the anterior half of the 

 dentary bone of a small species of the characteristic Cre- 

 taceous fish, Pachyrkizodus^ and the resemblance of the den- 

 tition to that of the pleurodont lizards is merely a case of 

 analogy. 



The jaw exliibits the characteristic fibrous texture of fish- 

 bone, and the dentition is such as might from present knov,^- 

 ledge be assigned either to fish or reptile ; the bone does not 

 taper anteriorly, but, when viewed from beneath *, it siiows 

 the marked inflexion at the symphysis observed in all species 

 of the genus just mentioned. The arrangement of the teeth 

 agrees precisely with that described by Cope f and the present 

 writer % in PachyrJuzodus ; and the dentition is so closely 

 paralleled by that of a maxilla in the British Museum asso- 

 ciated with scales and detached bones (no. P. 1808), that 

 there can be no doubt as to the generic determination. With 

 regard to its specific characters, the slenderness and form of 

 the dentary bone are sufficient to distinguish it from all 

 described species of Pachyrhizodus^ and it may therefore retain 

 the name of suhulidens originally proposed by Owen. The 

 British Museum fossil just mentioned is also interesting as 

 extending the known range of the form to the Chalk of 

 Sussex. 



The intricate history of the acquisition of our knowledge 

 of Pachyrhizodus has already been summarized and discussed 

 in the ' Synopsis ' quoted above. Other supposed Saurians 

 —Mosasaurus gracilis and Acrodontosaurus Gardaeri — have 

 likewise been recorded through a misinterpretation of portions 

 of jaws of this great predaceous fish ; and it is unfortunate to 

 have to add one more of the few Reptilian generic names in 

 the list from the European Chalk to the synonymy of the 

 same deceptive generic type. 



* PI. xxxix. fig. 1, in "Dixon's ' Geol. Sussex.' 



t E. D. Cope, " Vertebrata of the Cretaceous Formations of the West " 



(U. S. Geol. Surv. Territ. 1875), p. 2i^0. 

 J Smith Woodward, luc. cit. p. 313. 



25^ 



