MIOCENE PERIOD 163 



sheep, with an outward appearance of coneys grown to 

 gigantic dimensions (Nesodon). 



Other allied forms have been named Astrapotheres, or astrapo- 

 " hghtning-beasts " ; and they must have presented a start- theres 

 Hng appearance. They were as large as rhinoceroses ; and, 

 though not related to those animals, they probably, bore an 

 outward resemblance to them. Some of the brutes were 

 provided with a pair of long and powerful tusks in the lower 

 as well as the upper jaw ; and the tusks were so brought into 

 contact as to ensure a mutual sharpening. As the monsters 

 were vegetarians, one may suppose that their well-stropped 

 blades were chiefly used in quarrels about females. 



Here also were other hoofed animals known as Litopterns litopterns 

 — a name having reference to an anatomical feature of the 

 heel-bones. They were for the most part long-necked crea- 

 tures, nearly as big in some cases as lamas, and the majority 

 of them were not unlike those animals in general appearance 

 (Oxyodontotherium). Their feet, as a rule, were three-toed, 

 and all the toes were in use. In some rather short-necked 

 and somewhat horse-like forms the " extra " toes had be- 

 come dwarfed and useless (Proterotherium), as was the case 

 with many of the horses then living on the northern con- 

 tinent. There is, therefore, no doubt that, in regard to the 

 feet, these animals and the horses were converging in de- 

 velopment. Indeed, a few of them were in that respect in 

 advance of the horses ; for they had quite lost their side- 

 toes, and were toed, therefore, like the modern horse 

 (Thoatherium). They were, however, far inferior to the 

 horses on the neighbouring continent not only as regards 

 fiexibihty of limb, but also in tooth-structure and brain- 

 power. 



Yet other animals, known as Typotheres, were perhaps typotheres 

 the most curious of aU (Pachyrucus). They were about the 

 size of hares, and probably looked like guinea-pigs much 

 overgrown. Mr. Lydekker has shown that they were more or 

 less closely allied to the Toxodonts, and so belonged to the 

 hoofed Order. They had, however, by a series of modifica- 

 tions, converged to the rodent type, as regards teeth and 

 toes, and also in other respects. The squirrels, hares, and 



