222 Prof. R. Owen on rare Extinct Vertebrates. 



explanation which I hazarded I believed might apply to ana- 

 logous instances in time-series of other and terrestrial herbi- 

 vorous mammals. 



The Coryphodons may have roamed over the regions of 

 Utah, Wyoming, and New Mexico in vast herds ; but they 

 were not harried and disturbed by the enemies that now per- 

 secute the bisons of North America. The instincts which 

 such unintermitting persecution have developed in the wild 

 Herbivora of that and other continents, and which call for 

 the utmost skill and w^ood-craft of the sportsman to circum- 

 vent, were little, if at all, excited in the oldest Eocene period, 

 so far as the evidences of contemporary enemies of Corypho- 

 don have come to light. 



" The brain-cavity in Coryphodon " (PI. XI. fig- 3, e^p, r), 

 writes Prof. Marsh, "is, perhaps, the most remarkable feature 

 in the genus, and indicates that the brain itself was of a very 

 inferior type ; but its most striking modifications are the small 

 size of the hemispheres [^] compared with the expanded cere- 

 bellum [fj]. The olfactory lobes [r] were large and entirely 

 in advance of the hemispheres " *. 



Thus the parts of the brain which experimental physiology 

 has associated with the locomotive function and the testing of 

 food, were present in due proportion to the bulk of the extinct 

 Herbivore. The quest of favourite foliage and delicate her- 

 bage by the exercise of an acute sense of smell, and the 

 migrations from pasture to pasture or from grove to grove, 

 were both provided for in their relations to the cerebral orga- 

 nization. But the superadded mass which converts the sen- 

 sations into ideas, and retains the impressions as memories, 

 remained at that low stage of development which suited a 

 blissful condition of existence untroubled by the necessity 

 of taking cognizance of, and contriving escapes from, the 

 attacks and wiles of creatures concerned in killing Corypho- 

 dons. 



To the close and careful comparisons of the conscientious 

 palaeontologist of Yale College we are indebted for the above 

 interesting and unexpected additions to our knowledge of the 

 rare and ancient Tertiary mammal, fragmentarily indicated 



increase in tlie niunber of creatures and their lethal powers concerned in 

 killing sea-cows would add to the niunber of phenomena which such sea- 

 cows were concerned in noting, with concomitant reaction of such per- 

 ceptions, or neural vibrations, resulting in a change of cerebral into 

 muscular force, exercised to put themselves into depths of safety. With 

 such augmentation of ideas the thinking-organ has grown." ("On Eothe- 

 rium fegyptiucnm,'' Quarterly Journal of the Geological Society, 1875, 

 vol. xxxi. p. 105.) 



• Marsh, lor. cit. p. 82. 



