276 ALOUATTA 



color, varying but slightly in the depth of the red ; one male not pro- 

 cured by Robert was obtained at St. Catherines and agrees with the 

 others in color, and a young $ from San Sebastian, Sao Paulo, was 

 obtained from A. Hempel. The skulls, however, do vary very much, 

 the differences when of the same sex, probably caused by age. Com- 

 paring the skulls of two adult males the shape of the braincase at once 

 attracts attention, where in one it is shorter and flatter above, with two 

 ridges starting from the center of the upper edge of the orbit, curving 

 towards the center of the skull, but keeping 20 mm. apart, and ter- 

 minating on the edge of the occipital on either side of the interparietal. 

 Another, with a longer braincase, has these ridges coalesce and form a 

 ridge or low crest down the center of the skull, broadening out in the 

 rear, and terminating at sides of interparietal. These two formations 

 so totally different occur in adult males from the same locality. These 

 skulls also exhibit differences which might possibly under other con- 

 ditions be taken as suflficient to cause a specific separation. The 

 premaxillaries in the longer skull extend forward beyond the canines, 

 coming to almost a point in the center, causing the alveolar border of 

 the outer pair of incisors to be lower than that of the middle pair, while 

 in the other skull the alveolar border of the incisors is perfectly straight, 

 causing the width between the canines to be much greater, nearly 4 

 mm. Other differences are also observable, such as in the width of the 

 pterygoid processes, the width of the basi-occipital, length of the ptery- 

 goid fossa, width and shape of the palatal arch, width and shape of the 

 occipital region, and the curve of the frontal and nasals, all these, with 

 others not mentioned, serve to show the great individual variation that 

 exists in the skulls of this species even among animals of the same sex, 

 and practically the same age, dwelling in the one locality. A larger 

 series would undoubtedly show greater diversities. The young of this 

 species are jet black, the golden brown appearing on the tips of the 

 hairs as they grow older, this gradually extending from the head to 

 the body and limbs, and growing more and more red until in the fully 

 adult the pelage assumes the appearance as described for the males 

 given above. Mr. Robert's series from Roca Nova, Parana, exhibits 

 this change finely. This is the style that has been described as distinct 

 by Kuhl as Mycetes fuscus. 



Alouatta (Simia) flavicauda was described by Humboldt (1. c.) 

 from the Province of Jaen. He did not see this Howler living, but 

 describes it from some skins procured by natives, and no specimens 

 answering to this description have ever been received by any Museum. 

 Its peculiarities are the extremely long hair on the body, and the color 



