SKELETON OF QUADRUMANA. 539 



both pairs of limbs are concerned in support and locomotion ; but 

 are made prehensile in relation to an arboreal sphere of life by 

 an opposable thumb-like condition of the innermost of the five 

 digits, always conspicuous upon the hind-limbs, and, in most, upon 

 the fore-limbs. Complete clavicles, and an elbow-joint allowing 

 both rotatory and flexile movements of hand and fore-arm, are 

 present in all. 



The scapula of CMromys^ fig. 343, 5i, differs from that of Rodents, 

 and resembles that of Lemurs, in the proportions of the pre- and 

 post- spinal fossae. The subscapular surface does not show the inter- 

 muscular cristiB which are usually so well marked in Kodents. 

 The length of the acromion, a, is 6 lines ; that of the coracoid is 7 

 lines : it is a simple compressed process. The glenoid ca\ity is a 

 long oval, with the apex above and rather produced. The clavicle 

 has a double bend upward and outAvard, and a half twist on itself. 



The head of the humerus, 53, has a long-oval form, regularly 

 convex, and surpassing in both breadth and length those dimensions 

 of the glenoid cavity. The great tuberosity projects on one side 

 to the same height ; the small tuberosity is somewhat lower. A 

 sharp deltoid ridge extends from the fore part of the great tube- 

 rosity halfway down the shaft. The supinator crest begins belov/ 

 the middle of the shaft, near its back part, standing well out, and 

 thence passes in an almost straight line to the ectocondyloid tube- 

 rosity. The internal ridge projects from nearly the fore part of 

 the distal fourth of the shaft, bridging over the humeral artery 

 and median nerve on its way to the entocondyloid tuberosity 

 where it coalesces with a shorter and sharper ridge, completing 

 the epicondyloid foramen. The inner tuberosity is much more 

 prominent than the outer one. The anconeal fossa is oblong, 

 of moderate depth, and imperforate. The tubercle for the radius 

 forms nearly half of the fore part of the elbow-joint ; the back 

 part is exclusively formed by the well-defined trochlear cavity 

 for the ulna. The humerus reaches to the tenth rib, when bent 

 upon the chest : and this proportion of length is characteristic of 

 most LemuridcB. 



The radius, 54, is of equal length Avith the humerus ; the head is 

 nearly circular. The ulna, 55, is the longest bone of the fore-limb : 

 it is compressed below the humeral joint, and gradually narrows 

 to the lower fifth of the shaft. 



The wrist-bones, 56, are ten in number, including a supplemental 

 sesamoid on the outer side of the scapho-trapezial joint. The 

 scaphoid is the longest, presenting its convex articular surface to 

 the outer two thirds of the radial concavity, and articulating with 



