120 



MERISTIC VARIATION. 

 SUMMARY OF 40 CASES: Welcker 1 . 



[part i. 



(c. r., cervical rib. C 6 , C 7 , &c, sixth, seventh cervical vertebra, &c.) 



45. Choloepus. 



SUMMARY OF 9 CASES: Welcker 4 . 



1 Welcker, Zool. Anz. 1878, i. p. 294. 



2 This includes the celebrated specimen (in natural ligaments) described by 

 Rapp, Anat. Unters. d. Edent., Tubingen, ed. 1843, p. 18. 



3 This specimen is labelled C. didactylus, but coming from Ecuador and having 

 this formula is probably C. hoffmanni. (Compare Thomas, O., P. Z. S., 1880, p. 492.) 

 In it C 6 bears cervical rib articulating with shaft of the first thoracic rib. 



4 Zool, Anz. 1878, i. p. 295. 



5 In a specimen in Leipzig Museum, no. 459, the 6th cervical bears large ribs, of 

 which the right nearly reaches the sternum, so that Welcker says that there are 

 only 5 true cervical vertebras. In another of these specimens there is a cervical rib 

 on C 6 measuring 19 mm. 



