94 ME. G. BUSK ON THE ANCIENT OR 



publication of an excellent figure of the tooth in question by Professor Boyd Dawkins, 

 in his paper on B. leptorhinus {R. hemitoechus) ^. 



The above citation may suffice to show that in Dr. Falconer's opinion the Gibraltar 

 tooth belonged to the same species as that figured by Prof. Boyd Dawkins, which 

 is undoubtedly R. hemitoechus. 



Again, with respect to the molars. Dr. Falconer observes (op. cit. p. 329) that the 

 character which best distinguishes them from those of all other species lies in the 

 peculiar form of the " crochet " or promontory, projected forwards from the posterior 

 coUine into the transverse valley. " In all species, fossil or recent," he says, " except 

 R. hemitoechus, the ' crochet ' forms a plate, which is emitted at a very open angle with 

 the posterior coUine, and directed more or less diagonally towards the anterior outer 

 corner of the crown." Again (p. 331), " if the penultimate true molar in R. heviitcechus 

 be examined, the crochet presents a thick massive body thrown straight forward, and 

 forming an acute angle with the anterior margin of the posterior barrel. It is flat or 

 concave above [externally] and convex below [internally], narrow at the base, and 

 thickening to a blunt margin. In mass it bears a much larger proportion to the disc 

 of the hind barrel than in most of the other species. In the corresponding molars of 

 R. megarhinus, Christ, (pi. iii. fig. 5, of Christol's Mem., and pi. ii. fig. 5, Gervais's Pale- 

 ontol. Fran9.), besides the diS'erence of alignment in its offset from the hind barrel 

 the section of the crochet is wedge-shaped, thinning from a broad base to a sharp 

 edge " 2. 



But it is needless to say more with respect to the hemitoechine characters of the 

 Gibraltar teeth, so far as Dr. Falconer's opinion respecting them is concerned. Besides 

 the reference he himself gives to the specimen (B. M. No. 36770) figured by Prof. 

 Boyd Dawkins, the exact correspondence between the figure of m. 2 of R. hemitoechus 

 given in Paleontographical Memoirs, vol. ii. pi. xvi. fig. 1, with fig. 4, PI. X. of this 

 communication, cannot fail to satisfy us of the identity of the two forms, and of their 

 distinction from that presented by R. megarhinus, Christ. 



I have not thought it necessary to say any thing with respect to the points by which 

 the Gibraltar teeth are distinguished from the corresponding ones in R. tichorhinus, 

 the difi"erences in all respects being too marked to require comment. Nor, having 

 shown their apparent identity with those of R. hemitoechus, is it requisite to say much 

 respecting their distinction from the molars of R. etruscus, which species would other- 

 wise naturally have suggested itself as a very likely subject of comparison, nor 

 respecting their relation to the teeth of R. bicornis, which, again, might have suggested 

 itself as not unlikely to be found in company with //. crocuta. 



As regards R. etruscus, the figures and descriptions of the Gibraltar teeth already 



' Journal of the Geological Society, vol. xxiii. pi. x. flg. 5. 



' I am inoUned, from my own observations, to think that Dr. Falconer placed, perhaps, too much importance 

 upon the characters afforded by the " crochet," which appear to be very variable. 



