hrdliCka] skeletal REMAINS OF EARLY MAN 367 



of modern specimens. It is decidedly smaller than that of the anthro- 

 poid apes, but in monkeys the arch is again more flat. 



The middle jDart of the ventral surface of the posterior arch in the 

 Monte Hermoso atlas is so inclined that it- diverges slightly from the 

 vertical from below upward, just as in most modern human atlases. 

 But in all the apes and monke3^s examined this plane diverges in 

 exactly the other direction; that is, from above downward. 



The posterior tubercle in the Monte Hermoso specimen is rather 

 diffuse and is located in vertical direction about the middle of the 

 arch, as in most cases in man. In most of the apes, on the other 

 hand, this tubercle is most prominent at the lower border of the arch, 

 while farther above the bone surface is more or less flat or marked 

 by a depression. 



The atlases of anthropoid apes and of monkeys, mth rare excep- 

 tions in the goriUa, present a bony septum which passes from below 

 the posterior extremity of the upper articular facet to the posterior 

 arch, completing a canal for the vertebral artery and the suboccipital 

 nerve. A similar condition is still met with, on one or both sides, 

 in about 7.5 per cent of human atlases (Macalister) . In the Monte 

 Hermoso specimen there is no trace of this bony septum, a fact which 

 demonstrates in one more particular the unprimitive character of 

 the bone. 



The superior and also the inferior border of the posterior arch in all 

 the apes approximate more or less the straight line, while in the 

 Monte Hermoso atlas, as in many other human specimens, both 

 borders are concave on the sides and convex in the middle. 



The lateral masses can be described simply as stout, but they were 

 equaled or exceeded in all dimensions in more than 20 per cent of the 

 Indian atlases used for comparison. They are more noticeable in 

 this regard because they narrow somewhat the anterior half of the 

 central aperture. But their characteristics are the same as in man. 

 They are more nearly of the same height anteriorly and posteriorly 

 than in the anthropoid apes and monkeys, in which the posterior 

 portion is distinctly higher than the anterior, and their vertical axes 

 in particular show, as they do in most Indian atlases, a more mod- 

 erate inclination downward than in any of the lower Primates. 



The superior articular facets are not abnormal or other than 

 modern human in either their concavity, shape, or size, but the axis 

 of the right facet, owing mainly to its relative shortness, is less con- 

 vergent forward than usual. On the left side the facet was nearer 

 the more common form, being somewhat more prolonged forward. 



It is the lack of such a prolongation which causes the straightness 

 of the axis of the right facet. Such straightness is reached but sel- 

 dom in the Indian atlas, yet it occurs; and an examination of the 

 atlases of other Primates shows that it is not an approximation to 



