542 MR. J. w. DAVIS ON A [Jimc 23, 



Plate XLVII. 



Fig. 1. Rhacolepis huccalis, under aspect of head, showing ceratohyal {ch,), 

 epihjal (epfi.), and brauchiostegal ravs. [28900 a.] 



2. Ditto, tail. fP 1958 rt.] 



3. Ditto, pelvic bone. [P 1962.] 



4. Rhacolepis hrama, head, h nat. size. [15490.] 



5. Rhacolepis latzis, young iudiTidual. [P 1959.] 



All the specimens are preserved in the British Museum, and the numbers 

 refer to the Register of the Geological Department. Unless otherwise stated, 

 the figures are of the natural size. 



5. Note on a Fossil Species of Chlamydoselachns , By James 

 W. Davis, F.G.S. &c. (Communicated by Mr, A. 

 Smith Woodward, F.Z.S.) 



[Eeceived June 7, 1887.] 



Some years ago a Selachian was obtained by Prof. H. A. Ward, 

 which had been cavight off the coast of Japan. It was purchased 

 for the Museum of Comparative Zoology at Harvard College ; and 

 in January 1884 Mr. S. Garman, of that Museum, gave a pre- 

 liminary description of the fish in the 'Bulletin of the Essex Institute,' 

 vol. xvi., in which he recognized it as belonging to a new family and 

 instituted for it the genus Chlamydoselachus. A further contribution 

 was made to 'Science' on February 1st following, in which the 

 body is described as long and slender, compressed and thin towards 

 the tail ; five feet in length. The head is broad, slightly convex on 

 the crown ; six gill-openings are present ; the nostrils are nearly 

 vertical, with a fold dividing each orifice into two parts ; eyes 

 moderately large, without nictitating membrane. The mouth is 

 anterior and very wide ; the teeth are arranged in fifty-one rows of 

 six each across the jaws and are all alike. " Each tooth has three 

 slender, curved, inward-directed cusps, and a broad base, which 

 extends back in a pair of points under the next tooth, thereby 

 securing firmness and preventing reversion." The pectoral fins are 

 described as of moderate size, separated by a distance of twenty-four 

 inches fi-om the ventrals, which, along with the anal and caudal, are 

 large; above the anal there is a small dorsal. Mr. Garman con- 

 sidered that " a certain embryonic appearance in the specimen 

 necessitated a search among the fossils for allied species. Most 

 resemblance was found in the teeth of Cladodus of the Devonian ; 

 but the cusps were erect instead of reclining, and the enamel was 

 grooved instead of smooth." After the appearance of this notice of 

 the new fish, a considerable amount of correspondence took place in 

 the pages of ' Science,' and diverse opinions were expressed as to 

 the relationship of the genus to extinct forms. Prof. Cope considered 

 that the teeth figured by Mr. Garman " show the animal to be a 

 species of the genus Didymodus ( = Dij)!odus, Agass.), which has 

 hitherto been supposed to be confined to the Carboniferous and 

 Permian periods ; " and in the ' American Naturalist ' of April he 



