PElsGELLT — OS TILE AGE OE TUE DAETMOOB GEANITES. 11 



sists of a pair of cones ; the inner one being rudimentary, the outer 

 one of the same anteroposterior extent as the normal outer cone, but 

 lower and thinner, and oblique in its position." It is this accessory 

 lobe, which in the ruminant division of Artiodactyla is strongly de- 

 veloped. 



In the Amphiiragulus communis, from the lacustrine marls of Bon- 

 zon, near Puy-en-Velay, the accessory lobe is more outwardly and 

 obliquely developed than in Didymodon, and the same remark applies 

 to the Xiphodon gracile. 



I have been slowly led to the conclusion that the specimen in 

 question is not to be identified witli any of these genera, from the 

 lower Tertiary deposits. At the risk of burdening the overloaded 

 terminology of the fossil herbivorous Ungulates with a new name, I 

 have been* led to give it generic distinction. The specific name 

 Vauchisianum is derived from the locality. 



Should it be placed amongst the Artiodactyles, under which order 

 it seems to be categorized, its place will be found near to Dichobune, 

 Acotherulum, and Aphelotherium. At the same time, there is a cer- 

 tain resemblance to Tapir ul us, which should preclude us from confi- 

 dently denying that it may have perhaps formed part of the family of 

 small pachyderms, congeners of the great Lophiodontoid Perisso- 

 dactyles. 



ON THE AGE OE THE DAETMOOB GBANITES. 



By W. Pengelly, E.G.S. 



Though our science has risen above the stage from which she taught 

 that all granites are parts of the original crust of the earth ; though 

 she has advanced so far as to doubt whether, in all cases, the granitic 

 was the first phase of rock-existence which the materials composing 

 it assumed, and to entertain the question whether such recks may 

 not be the extreme form of metamorphism, which has obliterated ail 

 traces of an earlier condition ; and though she may prudently decline 

 to point out, in the large circle of her rocky acquaintances, one mass 

 of crystalline unstratified rock which, as such, can be proved to be 

 older than some known beds of mechanical origin ; it remains to be 

 the rule rather than the exception to meet with persons, frequently 

 well-informed, and not without an interest in geology, who still cling 

 to the notion, or allow it to cling to them, that every mass of granite 

 is a primitive rock, in the strict chronological import of the term ; 

 and represents a period in the earth's history prior to the possible 

 existence of sedimentary strata, or of organized beings. Indeed the 

 opinion that granite is, in all cases, a primary rock, has so large a 

 place in the public mind, that one might prudently hesitnte before 

 throwing such a question as " What is the age of the Dartmoor 

 granite?" before any audience having a very large admixture of the 

 popular element. 



