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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



[Nov. 21, 



the Vicugna, yielding additional evidence of the adult condition of 

 the animal, to that afforded by the absence of epiphyses. 



The antero-posterior diameter of the tibia, measured from the 

 posterior edge of the internal articidar facet to the anterior edge of 

 the crest of the tibia, is, in — 



M. Boliviensis. M. Patachonica. G-uanaco. Vicugna. 

 in. in. in. in. 



2-4 5-4 2-3 21, 



so that the depths of the proximal ends of the tibiae of the two 

 Macrauchenice have the ratio of 1 : 2|, which corresponds very well 

 with the proportions of the astragali, and • confirms the conclusions 

 already arrived at, as to the relative lightness of the limbs of this 

 species in comparison with those of M. Patachonica, and as to the 

 similarity of the proportions of the Bolivian species to those of the 

 Llamas. 



"What remains of the outer edge of the tibia is sufficient to prove 

 that the fibula must have remained unanchylosed to the tibia for a 

 much greater distance than in the Patagonian species. From the 

 manner in which the outer tuberosity of the proximal end of the 

 tibia is broken off, I am inclined to suspect that the fibula was 

 anchylosed to it at this point ; and perhaps, as in the Auchenice, its 

 proximal end was represented only by a bony style. 



TJie scapula is represented merely by a mutilated fragment, com- 

 prising the glenoid cavity and the adjacent parts. The spine of the 

 scapula is broken off, and the glenoid cavity is somewhat distorted 

 by the bending of one of its edges; but enough remains to show 

 that the bone must have agreed with the scapula of Macrauchenia 

 Patachonica in all essential respects, and that it therefore differed 

 very widely from that of the Auchenice. In size, however, it nearly 

 corresponded with the corresponding bone in the latter animal ; for 

 the greatest diameter of the glenoid cavity is 1*2 in., the same 

 measurement in the Vicugna being l'O, and in the Guanaco 1*6. 



The ulna. — The fragment of the ulna, consisting of part of the 

 olecranon process and of the sigmoid cavity, is so crushed, that I can 

 only affirm its general agreement in form with that of Macrauchenia 

 Patachonica, and in size with the same bone in the Llamas. 



Hie lumbar vertebra. — Of bones referable to this region of the body, 

 again, there is but a single fragment, of value only so far as it con- 

 firms the conclusions arrived at b} r the examination of the more 

 perfect fossils. It corresponds very well with the posterior half of 

 the centrum of the penultimate lumbar vertebra of M. Patachonica 

 in form, and with the corresponding vertebra of Auchenia in size ; 

 but the crest into which the middle of its under surface is raised, 

 and which is still sharper than that in the Patagonian species, 

 diagnosticates it at once from any of the lumbar vertebrae of the 

 Llamas. 



The transverse diameter of the articular face is 1-1 in., its vertical 

 diameter 0-9. The corresponding measurements of the antepen- 

 ultimate lumbar vertebra of M. Patachonica are 3-0 in. and 2-1 ; so 



