42 THE SHEEP AND ITS COUSINS 



As to the origin of sheep as a whole we are 

 still very much in the dark, practically all that is 

 known being that the group is a comparatively 

 modern one, which does not apparently date further 

 back in time than the early part of the Pleistocene 

 or the later part of the Pliocene division of the 

 Tertiary, or latest, geological epoch. 



Certain remarkable ruminants, with curiously 

 twisted horns, occurring in the Pliocene formation 

 of the Isle of Samos and known as Criotherium, 

 have been regarded as closely allied to sheep, but 

 it seems doubtful if the relationship is as close as 

 has been supposed, and it certainly does not indicate 

 direct ancestry. In an earlier part of the present 

 chapter ^ mention has been made of certain extinct 

 antelopes from the Lower Pliocene strata of Greece, 

 characterised by the spiral of the horns running in 

 the same direction as in those of sheep, and hence 

 called O'ioceros. Mr. Gaillard, who proposed this 

 designation, has suggested that these extinct ante- 

 lopes represent the ancestral stock from which sheep 

 were developed ; but further evidence is required 

 before this view can be definitely accepted. 



It will be unnecessary on this occasion to refer 

 to what is known with regard to the ancestry of the 

 family Bovidce in general, especially since I have 

 given a summary of this in another work.* 



' Supra, p. 14. 



' The Ox and Its Kindred, p. 34. 



