DESCRIPTIONS OF THE PAPILLARY RIDGES 67 



papillary ridges are well marked on the dorsal surfaces of the 

 pulp and up to the free edge of the short nails, and to their lateral 

 borders, and on the dorsal surface of the hallux these ridges 

 approximate very closely on the two sides, leaving only a small 

 triangular space at the base of the nail unoccupied. On the 

 palm and sole and digits the surfaces between the interdigital 

 pads are covered by numerous nodules of varying sizes, with 

 narrow grooves between them, presenting a very corrugated 

 appearance. On some of the larger of these nodules obhque 

 papillary ridges can be detected with a lens. These represent 

 an early stage of the more developed condition in which the 

 digits and palmar and plantar surfaces are covered with ridges, 

 disposed in various patterns on the eminences and spaces 

 between them, which are characteristic of the hands and feet 

 of the Primates. On the drawing of Lemur brunneus a small 

 portion of the digits is shown enlarged, and on Lemur catta 

 of the palmar surface, also enlarged, and in these positions 

 the ridges are obHquely placed. It should be noted here that 

 the papillary ridges of the palmar and sole of Lemur catta are 

 much more developed than those of Le)nur brunneus, and the 

 hand of the former more developed than the foot. This differ- 

 ence in the two forms has probably a connection with their 

 difference of organisation. 



Marmoset. — The patterns of the Marmoset are good examples 

 of the common monkey-type, with elliptic ridges on the terminal 

 phalanges, longitudinal and oblique on the rest of the digits, 

 palm and sole, except on the three interdigital pads, thenar 

 and hypothenar of the hand, and corresponding pads on the 

 foot. 



The Squirrel Monkey {Chrysothrix sciurea) is more highly 

 developed in regard to the patterns of the hand, and has trans- 

 verse ridges on the digits of hand and foot, and thus advances 

 a stage beyond the Marmoset, though in the same direction 

 of development. In this form there are also seen for the first 

 time among Primates ridges grouped in an arched arrangement 

 on the digits of hand and foot. 



Brown Sapajou. — Cebus jatuellus shows similar characters 



