MACACUS. 59 



vertebrse and 18 caudal = only forty-six vertebrae. The skeletons are ligamentous 

 and perfectly entire, even to the last caudal ossicle. The 13th rib of the former 

 specimen is a short straight bone, an inch in length. There are eight true ribs in 

 each. In /3, the mammillary processes appear on the lltli dorsal and in « on the 10th ; 

 in the former the anapophyses first show themselves on the 13th dorsal and gra- 

 dually decrease in size from the 3rd lumbar vertebra, these processes following a 

 similar course in the twelve-ribbed specimen, i. e., commencing on the 21st segment. 

 The caudal vertebrae gradually increase in length from before backwards as far as 

 the 8th, beyond which they again shorten. The last trace of the neural arch occurs 

 in the 5th caudal vertebra, on which the laminae are prolonged for only two-thirds 

 of its extent. In a there is a tubercular-like neural spine on the 1st caudal only, 

 but in /3 there is no trace of it. The transverse process of the 1st caudal has consi- 

 derable antero-posterior expansion, but in the succeeding vertebrae it gradually de- 

 creases, and disappears on the 6th. In both examples, chevron bones well developed 

 occur first between the 2nd and 3rd caudals up to the 5th and 6th, beyond which 

 they do not extend, although a pair of hyperpophyses can be detected for some 

 distance backwards. In both these females, the manubrium is followed by seven 

 osseous segments terminated by the xiphoid, which is much longer and more ex- 

 panded in |3 than in «. The sternal elements also immediately preceding the 

 xiphoid are considerably longer in the latter than in the former, in which the total 

 sternum is 3'36, whilst in /3 it is 3*66. The manubrium of /3 is unsymmetrical, 

 being larger in its left than in its right half, to the former of which the cartilages 

 of the 1st and 2nd ribs are together attached, whilst the opposite bears only the 1st 

 rib. The clavicle of /3 is a shorter and stouter bone than that of ^^ measuring 

 1*84 as compared with 2*08. 



The pelvis of a. has greater capacity and posterior breadth than /3, in which 

 the distance between the callosities at their middle is only -75, in a being 1*18, 

 while between the position of the ischial spines the pelvis of a has a breadth of 

 1'22 and /3 of 1*52. These little difi'erences, however, can hardly be regarded as 

 more than individual. 



These skeletons do not present any anatomical features which would entitle 

 them to be regarded as specifically distinct from M. rhesus. The existence of 13 

 dorsal vertebrae in /3 being associated with only 6 lumbar vertebrae shows that this 

 monkey, which in its external characters differs somewhat from M. rhesus, is by its 

 osteology more allied to it than a^ which, in its peripheral features, differs in no 

 respect from M. rhesus. I have referred to the existence of only 18 trunk vertebrae in 

 the latter specimen under M. assamensis, the Burmese example of which is also 

 distinguished by a similar number of trunk vertebrae. 



In three skeletons of M. rhesus in the Eoyal College of Surgeons in which the 

 tail is entire there are from 17 to 18 caudal vertebrae, the specimen No. 4991' having 

 the tail imperfect ; but as the foregoing monkey /3 has 20 tail segments, the varia- 



^ See Quart. Proc. Zool. Soc. 1875, p. 562. 



