1903.] ON THE CALLOSITIES ON THE LIMBS OF THE EQUID. 199 
Much smaller than the last species, the costule more distant, and 
densely marked with minute spirals. I can find no trace of these 
latter in D. skeati, but the single specimen was not taken alive. 
GEORISSA MONTEROSATIANA Godwin-Austen & Nevill. 
Georissa monterosatiana Godwin-Austen & Nevill, P. Zool. Soc. 
1879; p2729) pl. xs fie) 6: 
Hab. Perak. 
EXPLANATION OF PLATE XX. 
Figs. 1,2. Pterocyclos subalatus, p. 195. 
3. Diplommatina skeati, p. 198. 
4,5. Opisthostoma annandalei, p. 198. 
6, 7,8. Rhiostoma jalorensis, p. 196. 
9,10. Rhaphaulus perakensis, var. jalorensis, p. 197 
11,12. Rhaphaulus ascendens, p. 196. 
13, 14, 15. Lagochilus kobelti, p. 194. 
16. Diplommatina laidlawi, p. 198. 
17, 18,19. Ditropis caverne, p. 195. 
3. The Significance of the Callosities on the Limbs of the 
Equde. By R. LypexKer, F.Z.8. 
[Received February 5, 1903. ] 
The question as to what structures in other mammals are 
represented by the callosities on the inner sides of all the limbs of 
the Horse, and those of the hind-limbs of the Kiang, Ass, and 
Zebras, 1s one which has attracted the attention of many naturalists, 
nearly all of whom appear to be in accord in regarding them as 
vestigial structures. The late Sur W. H. Flower, for instance, in 
his work ‘ The Horse’ expressed the opinion that these structures 
are degenerate glands; pointing out at the same time that the 
so-called ergot on the hinder aspect of the horse’s pastern appears 
to represent one of the pads, or cushions, which are still functional 
in the foot of the 'Tapi. 
In his volume on ‘ Mammalia” in the ‘Cambridge Natural 
History’', of which the preface is dated February 1902, Mr. 
Beddard gives a qualified support to this gland-theory ; stating in 
one passage that the equine front callosities probably correspond 
to the carpal glands of several other mammals, although on 
another page their glandular nature is questioned. In an 
apparently later communication? the same gentleman suggests 
that the callosities on the fore-limbs of the Hguide may represent 
a carpal sense-organ, vestiges of which he believes to survive in 
the carpal bristles of the Dassies. The degeneration of such an 
organ would, it is urged, very likely result in the formation of 
structures resembling those under consideration. 
1 Pp. 12, 13, and 240. 
2 Proc. Zool. Soc. 1902, i. p. 135.—I am indebted to Mr. Beddard himself for 
directing my attention to this passage. 
