ANATOMY OF MEGAPTERA LONGIMANA. 39 



Relative Length of the Digital Bones. — Running the eye 

 down the columns of Table IV. it is seen that, in B. musculus, 

 the lengths diminish gradually from the metacarpal onwards in 

 the two long digits. But in Megaptera the first phalanx is 

 longer than the metacarpal in all the digits except digit III., 

 although its first phalanx is the longest of the first phalanges. 

 This is owing to the still greater excess in length of the meta- 

 carpal of digit III., the metacarpal and first phalanx of which 

 together exceed in length by 4| inches the two corresponding 

 bones of digit IV., although the total length of digit III. 

 exceeds that of digit IV. by only one inch. In digit II. of the 

 50-feet-long B. musculus the first phalanx is slightly longer 

 than the metacarpal, and in my more mature specimens of 

 B. musculus it is so in the case of both digits II. and V., in 

 the 65 to 66-feet-long specimen to the extent of from ^ to f inch, 

 but they present no other exception to the progressive diminu- 

 tion in length onwards. The exceptionally great length of the 

 metacarpal and first phalanx of digit III. in Megaptera, will be 

 referred to in connection with the adaptation of the nodes and 

 hollows of neighbouring digits. 



Form, of the Digital Bones. — In my more mature specimens 

 of B. TYiusculus the ends of the bones are concave towards the 

 nodes, especially from side to side, most marked at the first two 

 nodes of digit III. and the first node of digit IV., but most 

 marked at the first node of digit III. On the lateral digits the 

 bones are rather cut obliquely, so as to give a somewhat wedge- 

 shaped node, the base of the wedge towards the free margin. 



tained. The 7th bone of its digit III. was injured. In Table III. it is seen that 

 in the most mature B. musculus digits II. and V. had 5 bones each, digits III. and 

 IV. 8 bones each. In this Table, IV., the lengths are taken along tlie middle ; 

 the breadth and thickness at the middle of the shafts, where the bones are 

 narrowest. The breadth is from radial to ulnar, the thickness from flexor to 

 extensor aspect. To show the much greater breadth at the ends of each bone 

 than at the middle, I subjoin the following measurements, in inches, of the 

 breadths of each bone of digit III. of Megaptera, at its distal and proximal ends, 

 that of the proximal end jjlaced first : — 1st bone, 4|, 4| ; 2nd bone, 41, 5 ; 3rd 

 bone, 5i, 5x\ ; 4th bone, ^, 4| ; 5th bone, 3|, 4 Jjj ; 6th bone, SjV, 3| ; 7th 

 bone, 2^, 2| ; 8th bone, IJ, If. It is seen from these measurements that, with 

 the exception of the metacarpal, and slightly of the second phalanx, the expan- 

 sion is greater at the distal than at the jiroximal end. This is seen, and to a 

 more marked degree, on all the bones of digit IV. It does not apply, however, 

 to the 1st and 3rd bones of digit II., or to the 1st and 2ud bones of digit V. 



