CHAP. VIII. CAUSES OP EXTINCTION OF MAMMALIA. 143 



Among the elephant remains from St. Acheul, in M. 

 Garnier's collection, Dr. Falconer recognized a molar of the 

 Mephas antiquus, fig. 19, the same species which has been 

 already mentioned as having been found in the lower-level 

 gravels of St. Eoch. This species, therefore, endured while 

 important changes took place in the geographical condition 

 of the valley of the Somme. Assuming the lower-level 

 gravel to be the newer, it follows that the Mephas antiqmis 

 and the hippopotamus of St. Eoch continued to flourish long 

 after the introduction of the mammoth, a well-characterized 

 tooth of which, as I before stated, was found at St. Acheul at 

 the time of ni}' visit in 1860. 



As flint hatchets and knives have been discovered in the 

 alluvial deposits both at high and low levels, we may safely 

 affirm that man was as old an inhabitant of this region 

 as were any of the fossil quadrupeds above enumerated, a 

 conclusion which is independent of any difference of opinion 

 as to the relative age of the higher and lower gravels. 



The disappearance of many large pachyderms and beasts 

 of prey from Europe has often been attributed to the inter- 

 vention of man, and no doubt he played his part in hastening 

 the era of their extinction; but there is good reason for sus- 

 pecting that other causes co-operated to the same end. 'No 

 naturalist would for a moment suppose that the extermination 

 of the Gyrena fluminalis throughout the whole of Europe — 

 a species which coexisted with our race in the valley of the 

 Somme, and which was very abundant in the waters of the 

 Thames at the time when the elephant, rhinoceros, and 

 hippopotamus flourished on its banks — was accelerated by 

 human agency. The same modification in climate and other 

 conditions of existence which aff"ected this aquatic mollusk 

 may have mainly contributed to the gradual dying out of 

 many of the large mammalia. 



We have already seen tliat the peat of the valley of the 



