SKELETON IN THE FLYING LEMURS. 155 



that the skeleton with respect to the numbei- of caudal vertebra^ is 

 imperfect in any of the specimens examined, but that the skeleton of the 

 tail is finished off distally by an apparently rudimentary vertebra which 

 lacks the posterior moiety. The truth of this has been confirmed in. my 

 specimens by the use of the microscope. For example, caudal vertebrae 

 11 to 15 in specimen number 2, very much resemble, upon a casual glance, 

 some of the joints of the manus or pes, with a shaft and articular extrem- 

 ities. Xow the minute terminal vertebra of the tail in specimen number 

 2 (and in others) if compared with a phalangeal joint, appears to have 

 been broken in two at the middle of the shaft, or at a point that in reality 

 is the middle of the centrum of the vertebra. The + stands for this 

 "nib" or rudimentary terminal caudal vertebra in my specimens, ajjd 

 as such is entitled to recognition in the total count. (See figure 17, 

 plate T. ) 



' From an examination then of six individuals, three of Flower and 

 three here, it may be stated with certainty that the number of vertebrae 

 in the spinal column of Cynoceplialits, irrespective of species, is markedly 

 variable, after we pass the 7 cervicals, which are invariably present in all 

 specimens. There may be 13 or 14 thoracic vertebrae (bearing ribs) ; 

 from 5 to 9 lumber vertebrae; from 3 to 5 sacrals, or those that fuse 

 together to form the "sacrum ;" and, finally, from 14 to 19 caudals, which 

 in most cases possess in addition (a +) a rudimentarv' one at the termi- 

 nation of the tail series. 



Throughout the class Mammalia, even including man, the number of 

 caudal vertebrse present in any particular species is subject to considerable 

 variation. This becomes less and less the case as we pass from the tail to 

 the cervical division of the spine, where with but very few exceptions 7 

 is the rule. Manatus among the Sirenia has but 6 cervical vertebrae; 

 which is also the case with Cholaptis among the Edentates, while in the 

 same group (Edentata) Bradypiis possesses 9. At the present writing 

 no other exception to this rule is known to me in the class. 



The count may be made to vary, too, by the number we elect to repre- 

 sent the pelvic sacrum. In CynocepTialiis as in other mammals, man 

 included, the number varies also with the number that fuse together to 

 form the sacrum. Where they have thus coossified, the bones so united 

 have been here considered as sacral vertebras; 3 in two instances; 4 in 

 another. In man they vary from 4 to 6. 



All these facts led Flower ^^ to state that — 



It must never be forgotten that although the division of the vertebral cohimn 

 into distinct regions is convenient for descriptive purposes, at the contiguous 

 extremities of the regions the characters of the vertebrie of one region are apt 

 to blend into those of the next, either normally or as peculiarities of individual 

 skeletons. 



" Osteology of the Mammalia, 78. 



