Reviews — Prof. A. Gaudrij — The Evolution of Mammalia. 225 



present result from the necessity that the foot should evenly sup- 

 port the pressure of the body. In the latter the external digit is 

 rather more slender than the internal digit, and from this faot an 

 explanation is derived for the circumstance that in the Perissodac- 

 tyla the fibula rests directly on the tibia instead of articulating with 

 the calcaneum, as in the Artiodactyla. This leads to the articulation 

 of the calcaneum with the cuboid becoming smaller, and therefore to 

 the attenuation of the fourth digit, so that the whole weight of the 

 animal is thrown on the astragalus, which is carried by the navicu- 

 lare, which is itself carried by the third cuneiform bone, which sup- 

 ports the third or middle digit of the foot. Hence it follows that the 

 astragalus of the odd-hoofed types, which is flattened in front, is 

 modified from the type of the even-hoofed animals, and the same 

 conclusion is supported by a consideration of the other tarsal bones. 

 It is even less difficult to establish a common parentage for the two 

 groups by means of the teeth. These considerations raise the ques- 

 tion whether the basis of classification should be taken from the 

 divergent descendants which survive or have been elaborated, or 

 whether the geological evidence has not now rendered it imperative 

 to unite in one great group orders of animals which have hitherto 

 been regarded as having a wider separation from each other than has 

 here been set forth. 



The seventh chapter deals with the Elephants, Mastodon and 

 Dinotherium, all of which date from Miocene times. But slender 

 additions are made to current knowledge of these animals, and 

 while indicating the obvious similitudes of their teeth to those of 

 some living types, the author finds no palseontological grounds for 

 suggesting their parentage. 



Similar difficulties, arising from the imperfect way in which 

 their remains are known, beset the comparative study of Eden- 

 tates, Rodents, Insectivora and Cheiroptera, to which the next 

 chapter is devoted. Edentates are known in Europe, in the 

 Eocene and Miocene ; and in America they are only known from 

 the newest formations. Macrotherium, an enormous animal from the 

 Middle Miocene, might have been a climber. It had relatively small 

 hind-limbs, and claws drawn back towards the metacarpals, so as not 

 to impede progression on the ground. Ancylotherium from Pikermi 

 is intermediate between the climbing and walking Edentates. A 

 few Eodents occur in the Eocene ; in the Upper Miocene of Greece 

 we have Porcupines ; Hares in the Pliocene of Auvergne ; and 

 Beavers in the Upper Miocene ; all the extinct genera onlj^ differ 

 from those now living in minor characters. Hedgehogs, Shrews, 

 and Moles, are all represented in geological time ; Hedgehogs in 

 the Miocene of Auvergne ; Moles in the same locality, as well as 

 at the foot of the Pyrenees and on the Ehine ; Shrews are found in 

 the Bourbonnais ; some of the old Miocene forms are so much 

 generalized that PJesiosorex, for instance, was regarded as a Hedge- 

 hog by De Blainville. The Cheiroptera are very imperfectly known, 

 and give no evidence of their descent. 



The ninth chapter treats of the Carnivora. Here, especially, it is 



DECADE n. TOL. V. — NO. V. 15 



