448 DK. C. I. FORSYTH MAJOR OX 



Meyer's posthumous descriptiou of the E,ott skeletou, mention is made of upper molars 

 of Titanomys found isolated, but only one small outer root is ascribed to them. 

 I likewise find that the anterior milk-tooth, d- •^ , of the E-ott skeleton has one 

 small outer root. Almost all the isolated teeth at my disposal, of both species, 

 exhibit two symmetrical outer rootlets, which represent the lower free terminations 

 of two prominent ridges on the upper outer region of the tooth, as in the figured 

 deciduous tooth of Lepus PI. 39. fig. 9, b), with the difference that in the latter the 

 posterior part of the first appears higher, and the ridges, therefore, more lengthened 

 than in Titanomys. The ridges, of which the outer rootlets are the lower termina- 

 tions, are present also in molars and premolars of all Lagomorpha growing from 

 persistent pulps. Pigs. 7 and 8 (PL 39), representing germs of the first upper true 

 molar of a rabbit, show them in side view (at the right side of the figures). 



In a left ujjper jaw of Titanomys Fovtaunesi the roots of the cheek-teeth are 

 described in the following manner by Deperet : — "La disposition des racines est 

 aussi tr^s particulifere, et differe de ce que Ton voit chez les Leporides pour se 

 rapprocher d'autres groupes de Rongeurs tels que les Spermophiles. Chacune des 

 quatre dernieres molaires porte trois racines, dont une interne grosse, ovalaire trans- 

 versalement, et deux externes relativement tres petites et arrondies. L'alveole de 

 la premiere molaire est petit et rond : il annonce une molaire uniradiculee et a 

 couronne assez petite " *. The figure of tlie sjiecimen f shows the empty alveoli of 

 p. 2 and m. 1, so that the mode of disposition of the roots in the jaw can be seen. 

 Deperet's description is confirmed and supplemented by the figure which I give 

 (PL 36. fig. 23) of a left maxillary from which the teeth have dropped out. 



P. 2 of Tit. visenoviensis, the anterior lobe of which we have seen to be somewhat 

 reduced antero-externally (PL 36. fig. 19), as compared with the posterior teeth, has 

 only one outer rootlet (PL 39. fig. 5«) ; in the place of the antero-cxternal rootlet 

 it displays a citrious conformation, which gives at once a clue to that of the rootless 

 molars of the other lagomorphous genera, and explains why the upper teeth described 

 by H. V. Meyer have one outer rootlet only. There is no free antero-external radicle 

 to this tooth ; bvit, as seen in the side-view (fig. 5 a, PL 39), a raised ridge runs along 

 its antero-external side down to the bottom, where, as shown in the lower view of 

 the tooth (fig. 5, t)), it is confluent with the lower opening of the large inner root, 

 the homologue of the widely open cavity in the genera {Lagopsis, Prolagus, Lagomys, 

 Lepvs) with rootless teeth. 



To judge from its alveohts, p^ of Titanomys Fontannesi was more like p. 1 and tlie 

 true molars, than p^ of Tit. visenoviensis. 



Pig. 2, PL 39. represents [a) the anterior, and {!)) the outer view, of the last upper 

 molar, riirht side, of Tit. Fontannesi, the iijiper view of which has been figured in 

 PL 36. fia'. 6. Both outer rootlets are broken off, but they seem to have had a free 



* Cliarlts Dqioret, "Eoch. nii- ]:i S^iiccession des Faiiucs de Vnt. llioci'Ees, etc.," Arc-b. Mus. Hist. Nat. Lyon, 

 t. iv. 1). 171 (1887). 



t Oj-i. (it. pi. xiii. fig. 10. 



