228 Scientific Proceedings^ Royal Dtihliii Society. 



width are almost constantly, and the width of the brain-case very frequently, 

 greater proportionally in L. vanabilis typicus, as compared with the corre- 

 sponding measurements in L. europmis, and that the diastema is usually 

 proportionally shorter, and the molar series proportionally longer, in the 

 former species than in the latter. 



Turning now to the fossil skulls from Ightham, that in the collection of 

 Messrs. Corner and Kennard is associated, as already stated, with the greater 

 part of the skeleton. Except for the fact that the nasals are wanting, it is 

 perfect, and has all the teeth in place. The general form, the little constricted 

 temporal region (PL XV., figs. 1-4), the form of the anterior part of 

 the zygoma (PI. XV., fig. 4), the measurements recorded in the 

 Tables 1-3, as well as the characters yielded by the dentition and lower 

 jaw, to be discussed later, all agree in proving this skull to be referable to 

 a form of L. variabilis. 



The skull in the collection of Mr. Lewis Abbott is a little larger than that 

 just described ; and it comes from a somewhat older animal, the sutures being 

 more tightly closed. The zygomatic arches are broken off just behind their 

 maxillary roots ; and the upper rim of the right orbit is broken away. The 

 face has been crushed in, and not very skilfully restored, which may account 

 for some slight differences in the proportional measurements. In form this 

 skull agrees perfectly with the fossil already described ; and it is referable to 

 a form of L. variabilis. The nasals, which are here fortunately preserved, 

 enable us to complete the comparison. Their greatest length is about equal 

 to the length of the sagittal suture of the frontals, and their upper surfaces 

 are sharply bent upon the planes of the outer surfaces (PI. XV., fig. 5). 

 The foremost upper incisors distinctly extend backwards into the maxillaries. 



Sanford long ago described a fossil skull from one of the Somerset 

 caves,' referring it to L. diliivianus, Pictet.- He pointed out that the 

 zygoma and superciliary processes were much as in the Polar Hare [L. var. 

 arcticus) ; and it is evident from his figure that the skull in question is to be 

 referred to the variabilis group. A comparison of the Ightham skulls with 

 Sanford's figure shows that all three skulls are to be referred to one and the 

 same form, although the measurements recorded by Sanford, when reduced, 

 are somewhat different from those of the Ightham specimens — differences 

 which are, perhaps, best accounted for by the differences in the methods of 

 measurement employed. 



The large size of these fossil skulls is equalled only by that of the skulls 

 of the sub-species Jv. var. grcenlandiciis, L. var. ainu, and-t. var. tschuMscliorum. 



' Sanford, Quart. Jouni. Geol. Soc, vol. xxvi, p. 126, PL viii., fig. 5. 

 ^ PiCTHT, Traite EUmentaire de Paleontologie, 1844, t. i., p. 207. 



