6 ARKIV FÖR ZOOLOGI. BAND 8. N:0 19. 



The shape of the choana? in this latter Guanaco has some 

 resemblance to the same of the Vicugna from approximately 

 the same locality, but the agreement is restricted to this and 

 to the inflated state of the bulla?. The skull of a male Vicugna 

 of similar age is much smaller (conf. table of measurements), 

 the anterior palate is not so strongly constricted, the palatal 

 foramina are not situated in front of the premolars, the longi- 

 tudinal extension of the molars is shorter, but their trans- 

 verse diameter equal, or even greater, the nasals are shorter, 

 and the middle incisors of the lower jaw are very much narrower 

 than in the small Peruvian Guanaco. The foramina incisiva 

 of the Vicugna are short, about 9 mm., while their length in 

 the Peruvian Guanaco is 13,7 mm. There is thus no difficulty 

 in distinguishing the skulls of these animals from each other. 



The Alpaca skull has V-shaped choanse, diverging behind. 

 The anterior palate is rather broad measuring in a young adul- 

 male 13,5 mm. The molars of the Alpaca are larger than those 

 of the small Peruvian Guanaco. The foramina incisiva of the 

 former extend in front of the level of i s . The foramina pala- 

 tina sit on a level with m 3 , or even alittle in front of the same, 

 thus in this respect approaching the condition of the small Pe- 

 ruvian Guanaco. Another resemblance is that in the Alpaca 

 as well the distance from the back of the condyle to the ante- 

 rior brim of the orbit (130 mm.) is longer than the distance 

 from the orbit to the tip of the premaxillaries (120 mm.). 



The most striking difference is produced by the very great 

 breadth of the middle incisors of the lower jaw of the Alpaca, 

 the combined breadth of the pair of i t measuring a little more 

 than 24 mm. The second pair of lower incisors are also very 

 broad in the Alpaca each measuring about 11 mm., while the 

 corresponding measurement of the small Peruvian Guanaco 

 is only 8,2 mm. In the much larger Patagonian Guanaco i 2 

 is of ten broader than in its small Peruvian relative, but the 

 greatest breadth observed in any of my specimens is, however, 

 only 10 mm., thus less than in the Alpaca. In consequence 

 of the very great breadth of i t and i 2 in the latter animal these 

 teeth must to great extent overlap in such a way that about 

 half the breadth of i 2 is pressed close the inner side of i v The 

 incisors of the Alpaca thus form a much more powerful and 

 broader chisel-shaped tool than in the Guanacos, not to speak 

 of the Vicugna, in which these teeth are placed so that », does 



