72 Proceedings of Royal Society of Edinhurgh. [sess. 
an imossified pisiform cartilage was also present. As regards the 
digits, four were present. Three of these, corresponding to a, h, and 
c in the description of the adult, were placed close together and 
parallel to each other ; but the fourth, or most ulnar digit d^ was 
set at an angle to digit c, so that an interval 1 J inches wide occurred 
between its terminal phalanx and the phalanx of digit c, to which 
it was opposite. On the other hand, the intervals between digits a 
and 5, and 6 and c, did not exceed a quarter of an inch. The exist- 
ence of the well-marked interval between c and c?, and the divergence 
of c, made me think that a rudimentary digit might be found in 
the intermediate structure. Accordingly, I dissected off the dried 
integument with care, but failed to see any osseous or cartilaginous 
structure in the interval. 
As regards the general morphology of the carpus in B. rostrata, 
the proximal row presents no difficulty, for it possesses the three 
bones customary to the Cetacea, with in addition a pisiform. The 
distal row, as is generally admitted where only two distal carpalia 
exist, presents more difficulty. So long as it was thought that the 
missing phalanx in the cetacean tetradactylous hand was the pollex, 
it was natural to consider that the trapezium Cj was also absent, 
or was fused with the radiale, and that the two distal carpalia repre- 
sented, the one C2 + C3, the other -f C5. The recent discovery by 
W. Kiikenthal * in an embryo Balsenoptera of a rudimentary digit 
lying in the interval between the phalanges of digits b and c, raises 
the question whether it is not the middle digit, medius, rather than 
the pollex, that is absent in the manus of the Eorquals. Should 
this be so, the four digits would then represent the pollex, index, 
annularis, and minimus. It is, therefore, possible that the os 
magnum, carpale 3, as the distal carpal belonging to the medius, 
may, like its digit, be suppressed ; that carpale Ca may represent 
both trapezium and trapezoid C;^ -f C2, or possibly only the trapezoid 
C2, Cj being fused with the radiale ; whilst Cf3 may represent the 
unciform, carpalia 4 and 5. C4 -f C^, owing to the suppression of 
the os magnum, lies more to the radial side of the carpus than is 
customary, so as both to articulate with carpale 2, and to allow a 
portion of the metacarpal bone of the most ulnar digit to articulate 
with the ulnare of the proximal row. This is, however, merely a 
* Anatomi&cli&r Anzeiger, December 27, 1890. 
