DR. J. MURIE ON THE ANATOMY OF THE WALRUS. 449 
other short tendons divaricating from it, one to either side and one immediately beneath 
the said mesial tendon; two of these proceed obliquely outwards and are inserted into 
the proximal end of the last phalanx, where they are continuous with the lateral 
binding fascia of the digit; the third terminates about the middle of the bone of the 
last phalanx. 
The tendon derived from the palmar expanse of fascia which goes to the pollex 
slightly differs from the preceding in terminally not splitting into four, but continues 
singly to the root of the digital cartilage. 
There is no trace whatsoever of the flexor brevis minimi digiti so well developed in 
the Otaria jubata, Phoca fetida, and P. vitulina. 
On the contrary the Walrus has a pollicial muscle, wanting in the Sea-lion. This 
appears to be the homologue of the opponens pollicis (woodcut 5, op.p). It has origin 
at the proximal end of the first metacarpal, and lies along the whole radial side of this 
bone. ‘The fleshy portion, very moderate in quantity, stops short about the middle of 
the bone; but tendon is carried on and is lost in the binding fascia. 
It may be remarked, as probably more influencing the flat plantigrade character and 
stiff unyielding nature of the manus of the Otavria, in contradistinction to the more 
flexible paw of the Trichechus, that in the latter the deep palmar fascia is by no means 
so large and strong as in the former animal. 
The portion superficial to the interossei, and extending lengthwise to the distal ends 
of the first and second metacarpals, which I have designated in the Sea-lion as the first 
part, and which gives rigidity to the great pollex, is wanting in the Walrus, or at least 
only represented by thin membrane, and thus permits much more grasping-power in 
the latter animal. ‘The second portion is equally thin and non-ligamentous. 
Sir Everard Home’ says there are no lumbrical muscles in the Walrus, though the 
interossei are, as he acknowledges, well developed; but my dissection revealed a single 
and very delicate lumbricalis in the fore paw (woodcut 4, Z.). On cursory inspection 
this was taken for a division of the flexor brevis manus; but it was found not at all to 
come from the upper surface of the palmar flexor fascia, but from its lower surface, 
quite apart from the other. ‘This representative of the lumbricales had origin on the 
pollicial side of the common fascia, and beneath the tendinous part going to the index ; 
from this by a very small fleshy belly it passed obliquely outwards, and with a long and 
very fine tendon was inserted into the binding fascia of the pollex at the inner distal 
end of the metacarpal, and partially in conjunction with the interosseous tendon. 
Another curious feature was the possession of a small palmaris brevis muscle. This 
was only of moderate thickness ; and its flesh had a breadth of half an inch, and a length 
more than double that. From its attachment, on the outside of the bone of the fifth 
digit, it as usual stretched palmar-wise on the surface of the superficial fascia. 
Interossei (woodcut 5).—It may be better to describe these separately, as they 
1 Phil. Trans, 1824, p. 239. 
