108 CHARLES MIDLO AND HAROLD CUMMINS 



Its individuality is indicated by the absence of formed ridges 

 in most of the prosimians, in Aotus and in Nasalis. A definite 

 parathenar pattern is commonly present only in Ateles and 

 Lagothrix ; it occurs infrequently in Alouatta. In the absence 

 of a pattern the parathenar area is usually evident as a more 

 or less discrete open field lying between the thenar and 

 hypothenar areas. This relationship is indicated in Pongo 

 (figs. 538-549), but in other catarrhines the parathenar region 

 may be absorbed by the expanded thenar and hypothenar con- 

 figurations, whether patterns (as in figs. 237-248) or open 

 fields (figs. 560-568). 



Sole. As in the palm, H d and H p may be present as two 

 separate elements or as one configuration. They are separate 

 in half or more of the available soles of Nycticebus, Pero- 

 dicticus, Galago, Oedipomidas, Saimiri, Aotus, Lagothrix, 

 Cebus, Papio, Pithecus, Erythrocebus, Pygathrix, Hylobates, 

 Pongo, Gorilla, Pan. Fusions of H d and H p are represented 

 by a single pattern situated at an intermediate level, a single 

 pattern seated in H d with its periphery blending into an open 

 field in the H p territory, or by a continuous open field extend- 

 ing over both regions. The genera in which half or more of 

 the soles are characterized by one or another type of fusion 

 of H d and H p are : Tarsius, Lemur, Callithrix, Alouatta, Ateles, 

 Pithecus, Lasiopyga, Erythrocebus, Hylobates, Symphalangus, 

 Gorilla, Pan, Homo. In Tarsius and Gorilla (one sole in each) 

 H d may fuse with IV, and in Nycticebus (two soles of six) 

 there may be fusion with IV f . In all soles of Tarsius there is 

 fusion of H p and Th to form a continuous open field; while 

 this does not differ fundamentally from the comparable con- 

 tinuity of open fields in some other genera, the topography 

 of the V-shaped ridged area, enclosing the ridgeless para- 

 thenar region, is worthy of note. 



In the material as a whole, excepting the prosimians, no 

 question arises with regard to the reality of two thenar con- 

 figurational units, Th p and Th d , but they exhibit so much 

 variation even within the same genus that it is difficult to 

 arrive at a statement of what constitutes their characteristic 



