TWO RARE MONKEYS. 389 



TWO RARE MONKEYS. 



By Dr. L. HECK, 



DIRECTOR OF THE ZOOLOGICAL GARDEN IN BERLIN. 



THE slender and the short-thumbed monkeys belong, in the 

 truest sense of the word, to an old simian family. The fact 

 is demonstrated as to the Indian slender monkeys, for indubita- 

 ble representatives of this genus (the Semnopithecus) lived in 

 the Tertiary period. 



The form of the skull gives the slender and short-thumbed 

 monkeys a peculiar appearance. It is roundish, the snout ad- 

 vancing but little in front of the forehead, and the bony crests 

 and edges, which often give the skull of the male an appearance 

 like that of a beast of prey, are hardly distinguishable. In a cor- 

 responding way the jaw is relatively only slightly projecting, and 

 less obvious in the slender than in the short-thumbed monkeys. 

 The entire skeleton in both groups is distinguished by the slen- 

 derness and lightness of its form, from which the slender monk- 

 eys get their name. The name of the African short-thumbed 

 monkeys relates to a peculiarity of their bony structure, in that 

 the thumbs of their fore limbs are not visible externally except as 

 stumps ; and, while in the slender monkeys, too, the thumb is 

 behind the other fingers in development, the complete arrest of it 

 in the others has been held sufficient to mark a distinction be- 

 tween the two families. On the other hand, I find a peculiarity 

 of the skeleton of the slender monkeys mentioned in only a few 

 descriptions, and in those casually, which appears to me as doubly 

 striking in the monkeys as climbing animals, and is not elsewhere 

 repeated in them, at least in those of the Old World. It is that 

 the slender monkeys have much longer and thicker hind legs than 

 fore legs ; the development of the hind limbs evidently surpasses 

 that of the fore limbs ; and this occasions characteristic deviations 

 in the attitudes and movements of the animals, as I have observed 

 daily with my pets. The slender monkeys run half erect with 

 their hind legs bent up, and make great leaps from this position 

 direct. Thus, notwithstanding their great agility, they have some- 

 thing hasty and angular in their motions, and maintain so pecul- 

 iar a gait that any one who has studied them continuously in 

 living specimens can distinguish at a glance whether a picture of 

 them is made from life, or whether it has been constructed by 

 adding a few special outward marks of the slender monkey to the 

 figure of a common monkey. In their inner structure the slender 

 monkeys and the short-thumbed monkeys have a highly important 

 peculiarity, unique in its way, in the shape of a composite, divided 

 stomach, suggestive of the ruminants, or rather of the kangaroo, 



TOL. XLI. 29 



