SKELETON OF QUADRUMANA. 543 



The humerus is not perforated either above or between the con- 

 dyles. The ungual phalanges are compressed and falcate, and the 

 pollex is on a line with the rest of the digits of the fore-limb, not 

 opposed to them. In the hind-limb the ungual phalanx of the 

 hallux is depressed for the support of a nail, and it is opposed as 

 a thumb to the other digits which have falcated ungual phalanges. 

 The ilium is long and narrow, with a supracotyloid ridge. In the 

 Marmoset ( CalHthrix sciureus), the pollex is partially opposable ; 

 as it is also in Cebus. In a young C. capucinus I have found the 

 humerus perforated both between the condyles and above the 

 inner condyle. There are fabellae behind the knee-joint. A sesa- 

 moid is wedo-ed between the entocuneiform and metatarsal of the 

 hallux. A pair of sesamoids are developed beneath the proximal 

 joints of each of the toes, and a single sesamoid beneath the last 

 joint of the hallux. 



In the Spider-monkeys (Ateles) the long and large coracoid 

 has an angular tuberosity, which sometimes joins the anterior 

 costa, so as to circumscribe the prescapular notch. The humerus 

 is not perforated either above or between the condyles. This 

 bone, and, still more, the radius and ulna, are remarkable for their 

 length and slenderness ; as are also the bones of the digits, wdth 

 the exception of the pollex, which is reduced to a rudiment of its 

 metacarpus, and is concealed beneath the skin in the recent 

 animal. The femur, tibia, and fibula are longer than in the 

 other Platyrrhines, but the tibia is not attenuated in the same 

 proportion. The inner border of the naviculare is much produced. 

 The thumb of the hind-foot is complete and well-developed. The 

 prehensile tail compensates for the loss of that quality in the hand. 



In the Catarrhine group the African Doucs ( Colohus) repeat 

 the abortive condition of the pollex ; but in all the rest it is a true 

 thumb, though smaller and weaker than that of the hind-hand. 



In the Baboons the coracoid shows an angular ridge, but less 

 developed than in the Capucins. In Macacus nemcstrinus the 

 short and broad coracoid has an angular tuberosity. I have ob- 

 served an intercondyloid vacuity in this species ; but, as a rule, 

 the humerus is imperforate at its distal end. The ' intermedium ' 

 is present in the carpus of all Baboons, Macacques, and Doucs, 

 as in the Gibbons and Orangs, fig. 361, A; and there are fabellie 

 behind the knee-joint. In most there is an ossicle, ib. i, wedged 

 between the scaphoid, «, and trapezium, d, in the wrist, and 

 between the cuboid and fifth metatarsal in the ankle. The 

 ischia expand into rough flattened tuberosities in all those Catar- 

 rhines that have the corresponding dermal callosities. 



