Shufeldt; Osteology of Lasiopyga and Callithrix. 81 



practically agrees with the facial angle of the skulls of Callithrix 

 jacchus now at hand. 



With respect to these skeletons, there is nothing like the differences 

 which are to be found in a'nd which characterize the skeletons of 

 Lasiopyga callitrichus and Lasiopyga griseoviridis, as set forth above. 

 The nature of these differences are well exemplified in the skulls of 

 these two specier of apes in the figures given in Plates XII-XV. 



The skeletal characters of the trunk and limbs in the case of Senioce- 

 bus practically agree in all particulars with the conesponding features 

 in any of the marmosets of the genus Callithrix; and in my opinion, 

 the fact of the matter is, in so fai as their osteology goes, there are no 

 constant characters to be found which justify the creation of different 

 geneia to contain these tamarins and marmosets. The lower canines 

 in a skull of Callithrix leucopus, as figured by Elliot (Plate XXVTI), 

 are exactly the same in character, both in form and in relative 

 lengths, as compared with the mandibulai incisors, as they are seen to 

 be in Seniocebus meticidosus (Plate XXII), or, as for the matter of 

 that, 'n Cercopithcciis midas (Plate XXIII) or in Leontocebus (Plate 

 XXIV) or CEdipomidas (Plates XXV and XXVI). All these animals 

 belong in the same genus, each presenting excellent distinguishing 

 specific characters, which characters are external rather than internal. 



According to Elliot (/. c, Vol. II, pp. 1-20) there are fifteen species 

 in the genus Aotus of the family Cebidce, they being known by the 

 vernacular name of Douroucoulis. They are chiefly nocturnal in 

 habit, and, "with one exception, A. rufipes from Nicaragua, Central 

 America, whose habitat is somewhat doubtful, the species of this 

 genus are found only in South America, and are distributed across the 

 continent from the Atlantic to the Pacific Ocean." 



Elliot figures the skull (four views) of but one of these species, 

 namely Aotus miriquoiiina (Vol. II, Plate I) and gives some of its 

 measurements (p. 11). There is a complete skeleton of this species in 

 the collections of the U. S. National Museum, and this I have before 

 me at the present writing (No. 103917 d^). 



The skull is quite different from the one figured by Elliot, it being 

 more elongate and veitically compressed, while the breadth of the 

 brain-case (35 mm.) is the same in each. In the skull which he figures, 

 however, the "occipito-nasal length" measures but 57 mm., while in 

 the skull belonging to the National Museum this diameter measures 

 67 mm. This is an excellent example of individual variation, in so 



