104 



MR. G. BUSK ON THE ANCIENT OR 



Dimensiona of astragalus in Hh'moceros. 



W 



tUD p 



N 



a) *- 



3 'a 

 e 9 



o a g 





■2 « 

 0.9 



Gibraltar, No. 1 



„ No. 2 



R. hemitcechus, Ilford, No. 22010, B.M. 



No. 20815, B.M 



, megarhimis, Grays, No. 21617, B.M. 



No. 21278 



, etriiscus, B.M 



, „ Malaga 



, tichorhinus, Brixham collection . . . . 



, bicornis {R. Jceitloa) 



, „ Saffron Waldron 



3-20 

 3-20 

 3-20 

 3-20 

 3-65 

 3-50 

 2-95 

 3-00 

 2-90 

 2-70 

 2-70 



2-70 

 2-65 

 2-50 



2-9 



2-5 

 2-5 

 2-5 



3-10 



3-15 



3-00 



3-30 



3-60 



3-50 



2-90 



3.00 



3-1 



315 



31 



2-30 

 2-37 

 2-37 



3-6o 



2'25 



2-5 



2-5 



3-1x2-1 

 x2-l 

 x2-3 

 X2-35 

 x2-5 

 x2-5 

 x2-0 

 x2-0 

 2-9 x 2-0 

 2-7 X 2-2 



2-5x1-6 

 xl-6 

 xl-6 

 xl-7 

 xl-9 

 xl-7 

 xl-5 

 xl-6 



2-5 X 1-65 



2-7xl- 



2-7x1 



xl- 



3-4x2- 

 3-3 x 2- 

 2-8 X 1- 

 2-6 X 

 2-9 xl' 

 2-8x1- 

 2-9 X 1- 



The mere inspection of the figures in these columns will show how very closely the 

 Gibraltar bones correspond in size and proportions with that of H. Jiemitoschus, or the 

 smaller of the Thames-valley species, and at the same time how widely in the main 

 they differ from any other of the species noticed. Had all the other characters been 

 equally in accordance, there would have been no occasion for any further comparison ; 

 but since, notwithstanding the remarkable resemblance in dimensions, the Gibraltar 

 astragalus offers some characters by which it would appear to differ not inconsiderably 

 from either S. hemitcechus or H. megarhinus (the only two with which it is at all worth 

 while to bring it into comparison), it will be necessary to add a few remarks. The 

 astragalus of M. megarhinus, besides its much larger size, is distinguished from that 

 of M. hemitcechus (from the Thames valley) by several peculiarities. 



1. The anterior or scapho-cuboid facet is more convex, and the proportional widths 

 transversely of the scaphoid and the cuboid segments different, the former being to the 

 latter as 1-000 to -405, whilst in R. hemitcechus the proportion is as 1-000 to -437. 



2. In R. megarhinus the outer calcaneal facet extends, with an even outline, quite to 

 the posterior and outer edge of the bone, whilst in R. hemitcechus the posterior border 

 of the facet is sinuous, a rough surface for the attachment of a strong ligament being 

 left between the margin of the facet and the postero-external border. 



3. In the astragalus of R. megarhinus the outer ridge of the trochlea is more rounded 

 or thicker than in R. hemitcechus. 



4. In R. hemitcechus the crescentic internal malleolar facet is continued close up to 

 the anterior border of the bone ; and there is little or no constriction between its 

 anterior termination and the scaphoid facet, whilst in R. megarhinus the crescentic 

 facet terminates at a distance of nearly an inch behind the border of the bone ; and, 

 corresponding with this, the upper arched border of the facet measured along the arc 



