QUADRUMANA. 



212 



which the inflated hyoid bone is situated. 

 The same character is to be found in the 

 genus Ateles. In Mycetes, Lagothrix, and 

 Callithrix, there is a peculiar round aperture 

 in the orbital portion of the zygomatic bone, 

 which has the appearance as if it were pierced 

 in the bone by a gimlet. Mycetes, Ateles, 

 and especially Callithrix, afford a very striking 

 conformity with Hylobates, in the swollen ap- 

 pearance of the posterior wall of the orbits, 

 produced by the convexity of the orbital part 

 of the zygomatic bone. This is a new addi- 

 tion to the analogy between Hylobates and 

 Ateles. The ala magna ossis sphcenoidei is yet 

 more depressed backwards than in Hylobates. 

 In Cebus (fg. 133) the cranium is elongated, 



Fig. 133. 



Skull of Celus apella. (Original, Mus. Vrollk.) 



and uniformly round. The frontal bone is 

 lengthened to a sharp point, which advances 

 between the two parietals. This is, as I have 

 said before, a manifest indication of a lower 

 rank. The face is not very prominent ; there 

 are two nasal bones ; a distinct intermaxillary 

 bone ; a rounded chin, which recedes. In 

 Callithrix, Pithecia, and Nochthora, the skull 

 has an oblong form, but it resembles very 

 much a small human skull. The single frontal 

 bone has a triangular form, and is distin- 

 guished by the convexity of the orbital part. 

 In the Saimiri the septum between the orbits 

 is but membranous, and the interorbital 

 space narrow ; the nasal bone is sometimes 

 single, sometimes double ; the intermaxillary 

 bone distinct ; the chin round and prominent ; 

 the muzzle not protruding ; the orbital part 

 of the zygomatic bone wants the opening 

 proper to Ateles, Mycetes, Lagothrix, and the 

 other species of Callithrix. This general re- 

 semblance to the human skull is still greater 

 in the Ouistitis. The external tuberosity of 

 the orbit is less marked ; the interorbital sep- 

 tum is osseous ; the muzzle not very promi- 

 nent; the intermaxillary bone distinct, but 

 obliterated in old age ; the nasal bones broad, 

 short, completely separated, and consequently 

 similar to those of man ; the chin is depressed, 

 but rounded. Notwithstanding this general 

 resemblance to the skull of man, Cebus, Calli- 

 thrix, and Hnpale differ in some essential 

 points from man. The forehead is much 

 narrower, and has its greatest elevation not 

 laterally, but in the middle ; the occipital fora- 

 men placed more backwards ; the muzzle more 

 protruding. In the vertebral column of all 



the Cebintz there is a manifest inferiority to 

 be seen in the disposition of the cervical ver- 

 tebrae, in which there are anterior ridges at 

 the transverse processes, in the same manner 

 as in the lower Mammalia. In the Cebi, the 

 spinal process of the second cervical vertebra 

 offers another analogy with the latter, in its 

 elevated form, in its strength, and in its 

 truncated posterior edge. In the Saimiri the 

 tendency to a lower degree of pefection is 

 still greater, by the triangular form of the 

 transverse processes, and in the Oiiistitis the 

 spinal processes become long, acute, and di- 

 rected backwards. The number of dorsal 

 vertebrae varies from 13 to 14, and is con- 

 sequently in general greater than in the 

 monkeys of the Old World. There is oppo- 

 site direction between the spinal processes 

 of the three last, and the ten or eleven first 

 dorsal vertebrae. The same disposition is 

 observed in the Saimiri, but in the Ouistitis 

 there is only opposition in the spinal pro- 

 cess of the last dorsal vertebra. In Ateles and 

 Cebus the number of lumbar vertebrae is five. 

 The styloid processes are plainly indicated, 

 but their spinal processes are inclined for- 

 wards, and terminate in a recurved point, 

 in the same manner as in the Carnivora. 

 In the Oiiistitis the analogy with the quadru- 

 ped form is still greater, as the styloid pro- 

 cesses are very long. In the Nochthora the 

 number of the lumbar vertebrae is eight, by 

 which it approaches to Stenops. The sacrum is 

 in the Ccbince a broad quadrangular bone, with 

 acute edges, united only by one of its spu- 

 rious vertebrae with the iliac bones. Conse- 

 quently the symphysis sacro-iliaca is less firm 

 than in the higher species of monkeys. At 

 least such is the case in the Cebi, the Ouistitis, 

 and the Saimiri ; but in Ateles I found four 

 spurious sacral vertebrae united with the iliac 

 bones. The iliac bones are in general nar- 

 rower in the Ccbincc than in the monkeys of 

 the Old World : consequently the pelvis has a 

 more cylindrical form, with a very long pubic 

 articulation, and approaches more to the 

 form of the pelvis in the Carnivora. The 

 caudal vertebrce of the Ccbince deserve a se- 

 parate mention. They are true or spurious ver- 

 tebrae. The true are but four or five, short 

 and thick. The spurious are the longest, but 

 become shorter at the extremity of the tail. 

 They are only united by the bodies, not by 

 the articular processes. Chiefly remarkable 

 are the inferior spinal processes in the an- 

 terior caudal vertebra', representing the letter 

 V, and forming a canal, in which pass the 

 vessels for the tail. These processes disap- 

 pear in general in the posterior caudal ver- 

 tebrae, and in the monkeys with a prehensile 

 tail the posterior vertebrae become round, 

 tubercular bones, imitating a series of small 

 digital phalanges. The thorax of the Cebince 

 is compressed, and the ribs do not form the 

 posterior arches, by which the back of man, 

 of the Chimpanzee, and of the Orang-cctan 

 acquire a broad and flat surface, and by which 

 it is possible for these animals and for man 

 to lie at full length on their back. All the 





