IS8 RODENTIA— OCHOTONID^ 



In the middle miocene Lagopsis a still further advance is 

 made, since the posterior upper premolar (/4) has completely 

 acquired the transverse arrangement ; the central upper pre- 

 molar (/s) being also in course of reduction. In Ochotona 

 (No. 5), the latter tooth, pi, in adult stages only retains the 

 internal crescentic fold b, having completely lost the outer one. 

 In LeporidcB this tooth also is fully transformed, and only the 

 anterior upper premolar (/a) retains any permanent trace of 

 the original pattern. Nevertheless, the milk-teeth, and the 

 unworn crowns of even the permanent teeth, of these highly 

 specialised modern forms still show ephemerally the ancient 

 pattern which characterised the teeth of their miocene ancestors, 

 as shown by No. 6, which represents a worn milk-molar of 

 a rabbit. 



Prolagiis is in another way of great interest. It makes 

 its first appearance in the middle miocene period, and species 

 are known to occur in the lower and middle pliocene deposits 

 of France and Italy. It is an extraordinary fact that a repre- 

 sentative of this tertiary genus, P. sardus, managed to survive 

 in the Mediterranean region until the pleistocene period 

 Remains of this rodent occur in great abundance in the bone 

 breccias of Corsica and Sardinia, and nearly allied forms have 

 been found in similar deposits on the shores of the Mediter- 

 ranean at Gibraltar, Cette, Rattoneau, Nice, and Mentone. 

 Forsyth Major proved indeed that in Corsica P. sardus 

 survived sufficiently long to have formed part of the food of 

 neolithic man.^] 



1 Prolagus, Pomel, 1853, antedating Myolagus, Hensel, 1856. See Forsyth Major, 

 Geol. Mag., October and November 1905, where numerous references to the literature 

 are given. 



Fig. 30.— Skull of Ochotona spelma, from Kent's Hole, Devon. (From Owen's 

 British Fossil Mammals, figs. 82, 83, and 84, p. 213.) 



