DERMATOGLYPHICS IN PRIMATES 101 



region, while platyrrhines evidence a lowering of the inter- 

 digital pads, carried to extreme degree in Ateles, Lagothrix 

 and, to a lesser extent, in Cebus. In this respect the three 

 genera named approach the conditions noted in Hylobatidae, 

 great apes and man. 



Pads Th and I are separate and distinctly elevated in all 

 prosimians except Nycticebus, where they are joined in a 

 common prominence as described above in palms. The Cal- 

 lithrichidae present in this region a narrow bolster, flattened 

 on the surface, representing a fnsion of Th and I. The only 

 sign of division of this elongated eminence, apart from the 

 dermatoglyphic expressions of its duality, is that it is cleft 

 transversely by a flexion furrow. The thenar pad in Aotus 

 is elongated and sometimes independent of I (fig. 2). In other 

 platyrrhines and in catarrhine monkeys Th and I are separate, 

 though Th is lowered and occasionally completely suppressed. 

 The Hylobatidae, Pongidae and Homo show flattening and 

 loss of individuality of the two pads. 



Plantar hypothenar pads present the following variants. 

 In Nycticebus, Perodicticus and Galago there is a single 

 elevation, more or less rounded, with no indication of two 

 components. Tarsius presents an elongated pad which fuses 

 distally with pad IV and proximally with Th. This bolster- 

 shaped pad is evenly elevated throughout its length, and is 

 devoid of signs distinguishing H d and H p . In Callithrichidae, 

 Saimiri and Aotus there is likewise a single elongated H pad, 

 elevated as a ridge and without indications of H d and H p . 

 In the simians not listed above, and in Lemur, the H area is 

 elongated, lowered and flattened. There is often a suggestion 

 of H d , evidenced as a slightly more elevated region; its 

 nature as an expression of H d is corroborated by the dermato- 

 glyphics. 



Accessory border pads. Only in Aotus are pads II r (IP) 

 and IV U (IV f ) distinctly separated from the respective adjoin- 

 ing interdigital pads II and IV. Even in this genus the four 

 pads are not consistently present, IP being the least common. 



