116 Olif THE TOMEEI^'E TEETH OE CTETfODUS. 



figures or descriptions of fossil teeth at all similar, either in their 

 external form or in their internal structure ; the teeth that most 

 nearly resembled them were certain varieties of JPetalochis 

 described and figured in Newberry and Worthen's Greological 

 Survey of Illinois, U.S. One palaeontologist whose knowledge 

 of fossil fish teeth is second to none, submitted that they might 

 be a variety ' of Petalodus, for in many respects their external 

 characters agreed with those of some teeth of that genus 

 discovered in America. So far as the outer appearances were 

 concerned I inclined to agree with this judgment, but when 

 I had made a microscopical examination I saw that in structure 

 at least, these teeth differed very much from the minute anatomy 

 of Petalodi teeth ; I, therefore, provisionally only, named these 

 new dental organs as pertaining to a fish of the genus JPetalo- 

 dopsis, and gave them as a specific name miral)ilis, on account of 

 the structure. A description of the external characters and the 

 internal structure appeared in " The Monthly Eeview of Dental 

 Surgery," for May, 1874, as one of a series of papers I was 

 publishing therein " On the Microscopical Structure of Fossil 

 Teeth from the Northumberland True Coal Measures." 



These two teeth were discovered on separate pieces of shale, 

 and were unaccompanied by any other remains, I, therefore, in 

 the above paper, hinted that Fetalodopsis was j)robably a Selachian ; 

 I also mentioned, however, that one of the features of the 

 internal structure was unlike any structure that I had seen in 

 the teeth of any fossil fishes, labyrinthodonts, reptiles, or 

 mammals, while the rest of the characters of the minute anatomy 

 closely resembled those of the mandibular and palatal teeth of 

 Ctenodus. As I had not at that time seen Ceraiodus nor read 

 Dr. Griinther's paper, I did not receive the hint that the latter 

 observation might have giveu me, viz., that the strange teeth 

 that I had named provisionally as Fetalodopsis mirahilis were 

 really the incisor or vomerine teeth of Ctenodus. It was 

 reserved for Mr. T. Atthey to make this observation, which he 

 did in the " Annals and Magazine of Natural History," for May, 

 1875, in a paper " On the Articular Bone and supposed Vomerine 

 Teeth of Ctenodus ohliqtms'^ ; he therein' says — " On a thin slab of 

 shale from Newsham (this is the pit from which I obtained my 

 specimens) in my possession, and which measures 5 by S^ inches, 

 are seen imbedded one rib, several bones of the head, fragments 

 ^of scales, and what I take to be right and left vomerine teeth of 

 Ctenodus.'" He then briefly describes the teeth, and closes his 

 remarks by stating that " the microscopic structure of these teeth 

 corresponds exactly with that of the maxillary teeth of Ctenodus. 

 I possess about a dozen other specimens believed to be vomerine 

 teeth of Ctenodus, in close proximity on the same slabs to the 

 bones of the head and teeth of Ctenodus.'' Mr. Atthey's 



