FOSSIL VERTEBRATES— MAMMALIA 1 85 



Pliocene mammals, near Trinil, in central Java. These are 

 believed to belong to one animal which has received the name 

 of Pitheca?ithropus erectus. The capacity of the brain-case is esti- 

 mated to have been about two-thirds the average of that of man : 

 the forehead is very low; and the supraorbital ridges are 

 prominent. The inclination of the nuchal surface of the occi- 

 put is considerably greater than in the Simiidas. The femur 

 measures 0.455m in length, and denotes an upright gait. 



" The oldest human skeletons of which the geological age is 

 determined with certainty, are two from the cavern of Spy, near 

 Namur, in Belgium. These were found in association with 

 remains of the mammoth and other Pleistocene mammals 

 beneath a layer of stalagmite, which had never been disturbed, 

 and which was also covered with earth containing bones of the 

 same extinct quadrupeds. The skeletons, therefore, could not 

 be the result of a comparatively recent burial, but were proved 

 to have been contemporaneous with the associated animals and 

 Palaeolithic flint implements. They are essentially human in 

 every respect, but seem to represent a race inferior in skeletal 

 characters to any now existing. They are small, but powerfully 

 built. The forehead is low ; the supraorbital ridges are very 

 prominent; and the chin is remarkably retreating. The radius 

 and ulna are unusually divergent in the middle. The femur is 

 somewhat bent, and the tibia is comparatively short, so that 

 the leg cannot have been quite upright in walking. This type is 

 now generally known as the Neanderthal race, the roof of a simi- 

 lar skull having been found associated with other fragmentary 

 remains so long ago as 1857 in a cavern in the Neanderthal 

 between Dusseldorf and Elberfeld, Germany." 



In closing the discussion of the mammals, it is well to draw 

 attention to the idea so forcibly set forth in Lydekker's book, 

 Geographical History of the Mammalia, that all the mammals had 

 a northern origin, and have attained their present position by 

 gradual migration toward the south. Though the theory is still 

 far from being proven, it should be of great interest to the 

 student of geology because of the possibilities it presents for an 



