1867.] BOYD DAWXINS EHnTOCEEOS LEPTOKHINUS. 217 



Cuvier, led him to infer that the leptorhine of Essex was identical 

 with that of Italy. The skull presenting a.j>artiaUi/ ossified cloison, 

 or bony partition between the nostiils, enabled him to amend Cu- 

 vier's definition of "R. a narines non cloisonnees" into "E. a narines 

 demi-cloisonnees," the name leptorliinus being retained because " the 

 nasal bones, notwithstanding their partial osseous supporting wall, are 

 actually more slender than those of B. tichorJiinus " *. The specific 

 identity of the lower jaws found in Italy with that found in Essex 

 is, indeed, open to considerable doubt : but, since the species of liJii- 

 noceros found at Clacton is one which I have traced widely in the 

 bone-cavems and river- deposits, and since its definition by Pro- 

 fessor Owen has been amply verified by recent discoveries, there 

 is every reason for the E. leptorliinus of Professor Owen being re- 

 tained as a specific name. Its identity with the E. leptorhinus of 

 Cuvier, from the conflicting evidence as to the presence of the cloison 

 in the skull which he constituted his type, is altogether a matter of 

 conjecture. 



2. Synonyms, — The Ehinoceros leptorliimis of Professor Owen is 

 the equivalent of the species mentioned by Dr. Palconer in his account- 

 of the Caves of Gower as E. hemitoechiis f, an undescribed and unde- 

 fined species that owes its existence to the translation of Professor 

 Owen's definition ' a narines demi-cloisonnees ' into a Greek specific 

 name. In central Prance it is probably identical with the E. meso- 

 tropus and E. Velaunus of M. Aymard %, the E. Aymardi of M. 

 Pomel§, and the E. leptorhinus (J)u Puy) described by 31. Gervais in 

 his * Paleontologie Erancaise'i!. 



The species is characterized by the possession of two horns, by the 

 partial ossification of the septum, by the slenderness of the bones, 

 and by certain peculiarities in the dentition, which I propose to de- 

 scribe in the following pages. In regard to the partially ossified 

 septum, it is intermediate between the tichorhine Rhinoceros, in 

 which the ossification is complete, and the megarhine, in which, 

 according to M. de Christol, there is no trace of a cloison. The de- 

 veloj)ment of this bony support for the nasals stands, as Cuvier re- 

 marked of it in the tichorhine Rhinoceros U, in direct relation to the 

 horn- development ; and therefore we may infer that also in respect 

 of the size of its anterior horn it was intermediate between the two 

 above-named species. 



The dentition of two out of the four British species of Pleistocene 

 Rhinoceros, the tichorhine and megarhine, has already been de- 

 scribed in the ' ]>7atural History Review ' ** ; that of the leptorhine of 

 Professor Owen merits a more careful examination than the rest, 

 because of its close resemblance to that of the megarhine, and the 

 wider range of the species in Britain than of the latter. The terms 

 and letters rendered necessary for its accurate description are those 



* Op. cit p. 368. t Quart. Journ. Geol. Soc.xyi. p. 489. 



X Pictet, Pal. torn. i. p. 298, sec. ed. (1853). 



§ Cat. Metb. 78, 1859. || Sec. edit. (1859) p. 90. 



^ Op. cit. p. 68. -"-^ No. XII. (1863). No. XIX. (1865). 



