A16

In Grays' Cat: of Br Mus (bones & skeleton the caudal vertabrae in Macacus differ from 24 to 3, the Barbary ape having only 3. In M. inornatus the tail is only 1 inch long and 1 ½ in circumference

Dr Murie will write about vertebrae
[Darwin wrote in Descent 1: 151: "Mr. Murie informs me that in the skeleton of a not full-grown Macacus inornatus, he counted nine or ten caudal vertebræ which altogether were only 1·8 inch in length. Of these the three basal ones appeared to have been embedded; the remainder forming the free part of the tail, which was only one inch in length, and half an inch in diameter. Here, then, the three embedded caudal vertebræ plainly correspond with the four coalesced vertebræ of the human os coccyx."

Gray, John Edward. 1843-1852. List of the specimens of Mammalia in the collection of the British Museum. London: By order of the Trustees. 3 vols. in 1 binding. CUL-DAR.LIB.68 PDF Darwin cited this in Descent 1: 150.