110 CHARLES MIDLO AND HAROLD CUMMINS 



quently in Nycticebus. Among the New World monkeys it is 

 seldom that fusions of II and III occur, though in Cebus about 

 one-fifth of the soles show no digital triradii separating these 

 areas when they are open fields. In the Old World monkeys 

 also the interdigital areas are typically not fused ; in Pygathrix 

 fusions of II and III and of III and IV occur rarely. In the 

 Hylobatidae there is characteristic blending of interdigitals 

 II, III and IV. Gorilla and chimpanzee frequently exhibit 

 this type of fusion ; it occurs rarely in orang and in man. 



The accessory border fields, IP and IV f , occur as patterns 

 only in Aotus. In Lagothrix they are distinctly limited from 

 the neighboring interdigital fields, though in no case is a 

 pattern found in them. Elsewhere throughout the primate 

 series the accessory border areas usually are absorbed by 

 the neighboring interdigital areas, though occasionally their 

 territories are indicated, in less marked degree than in 

 Lagothrix. 



Patterns in the distal portion of the central area (2 P , 3 P 

 and 4 P ) are sporadically and variably expressed. The oc- 

 currence of vestiges and patterns appears to be character- 

 istic in most New World monkeys (see especially Aotus, figs. 

 138-149), but only rarely in the other groups is there even 

 a questionable suggestion of their presence. 



The proximal part of the central area, the parathenar, 

 exhibits wide variation among the genera and even among 

 the individuals of the same genus. Some forms, including 

 most of the prosimians and Aotus, lack ridges in this area. 

 When the area is completely ridged it is seldom that a true 

 pattern is formed (as in figs. 37, 40, 412, 426, 428). In the 

 absence of a pattern the region may still be indicated, as it 

 commonly is at least in some individuals of all the remaining 

 groups. The parathenar area may be an open field dis- 

 tinguishable from the adjoining border areas only through 

 differences in ridge direction (e.g., fig. 43). Its distinctiveness 

 is usually heightened by the presence of bounding radiants 

 associated with it and the neighboring border fields (see 

 figs. 441-450). The parathenar area may be completely ex- 



