9° THE COLLECTION OF OSTEOLOGICAL MATERIAL FROM MACHU PICCHU. 



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Measurements of Skulls in millimeters. S 



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Greatest length 123 



Basilar length 99 



Zygomatic breadth 82 



Nasals 41 x 22.5 



Interorbital breadth 35 



Tip to tip of postorbital processes 49 



Least breadth above auditory meatus 37.5 



Greatest posterior breadth 47.5 



Occipital height from basion 28.7 



Length of broadened surface of zygoma 64 



Greatest height of zygoma 36 



Zygomatic concavity in horizontal plane 34 x 18 



Diastema 38 



Postpalatal length 38 



Length of upper tooth (crowns) 28 



Antero-posterior diameter of bullae 14 



The difference between most of the measurements of the two skulls are slight, but the 

 skull of A. thomasi is conspicuously longer in its greatest length and in its basilar length, 

 the latter dimension being presumably less subject to individual variation than the former, 

 which is obviously affected by the development of the occipital crest. The nasal bones of 

 A. thomasi are much longer as well as noticeably broader than those of A. sierra: and the 

 zygomatic concavities are wider. The bullae are of good size, having an antero-posterior 

 diameter of 15.5 mm. They are well rounded, not low nor depressed. The length of the 

 skull and the size and prominence of the bullae should be regarded as important characters, 

 since in the announcement of his A. sierra (loc. cit.) Mr. Thomas throws emphasis on the 

 smaller size of that skull and the xtry small size of its bullae. I quote from his summary 

 of the two groups of Paca : 



"To the lowland group belong the forms described as paca, Linn., fnk'us, F. Guv., subniger, 

 F. Cuv., and virgatus, Bangs, while to the highland series should be referred Tacsanowskii, 

 Stolzmann, and the present new form [A. sierra'], which may be identified by its small 

 size and very small bullae." 



The great distance — over a thousand miles^separating the known habitat of A. sierra 

 from the locality where this new species was found, taken into consideration with the 

 occurrence midway between of a form very different from either, naturally adds courage 

 to my conviction that the Paca inhabiting the Peruvian Andes centuries ago was distinct 

 from the species of Agouti hitherto described. 



