DR. J. MURIE ON THE ANATOMY OF THE WALRUS. 457 
the abductor minimi digiti. Thence it advances to the root of the fifth metatarsal, 
where it is tendinous and partially fixed thereon; but the muscle assumes a digastric 
type, inasmuch as from the above tendon, in reality a median one, a broad portion of 
_ flesh goes forwards and outwards, and at last is inserted into the outside of the fifth 
metacarpal along with the interosseus muscle of the same digit. 
There is a short, broad, and fleshy abductor ossis metacarpi quinti present (woodcut: 
fig. 8, Ab.o.m’). It has origin from the plantar surface of the calcaneum immediately 
beneath the flexor brevis minimi digiti. Its insertion by tendon is into the base of the 
fifth metacarpal bone. A representative of this muscle is met with in the Otary, 
though absent in the Seal. 
VIL. Fryat Remarks. 
In the subdivision of the Pinnipedia the majority of naturalists of recent times are 
inclined to look upon the Walrus as the sole representative of a family or subfamily of 
that group, the Trichecina of Turner (P. Z. 8. 1848). Trichechide of Huxley and 
others. Previously, in 1821, Dr. Gray used Trichechide as a family designation for 
this aberrant form; but in his late ‘Catalogue of Seals and Whales,’ 1866, he includes 
the Grey Seal (Halicherus grypus) and the Morse under the subfamily Trichechina. 
For the present I shall only say I incline to those who place the Walrus, per se, as 
the type of a family. Howsoever, as this isolation is based chiefly on the characters of 
the skeleton, which I have not treated of in this communication, I prefer to confine 
my résumé to such portions of the animal's organization as the foregoing dissection 
warrants. . 
I may however, en passant, quote Prof. Huxley’s’ lucid definition of the group and 
genus T'richechus:—1, skull narrowing more gradually forwards than in the other 
groups (Phocide and Otariide) ; 2, muzzle truncated ; 3, minute supraorbital processes ; 
4, palate extending back to the pterygoid processes; 5, tympanic even more ragged 
than in Otaries; 6, toes subequal in length; 7, astragalus normal; 8, two immense 
canine tusks in the upper jaw; 9, the fifth metacarpal does not articulate with the 
cuneiform; 10, an alisphenoid; 11, angle of mandible almost obsolete (as in Otariide) ; 
12, fifth digit of the foot the largest; 13, scapular spine further from posterior border 
than in Otariide. 
Whilst the above, without doubt, represent the most rigid taxonomic characters, yet 
there are others which may not be without value individually, or in the aggregate when 
a full review and comparison with other forms is instituted. Dr. Gray wisely uses a 
few of such external points in his synopsis of the tribes and genera. As an appendix 
to the preceding, they are :—1, hind limbs more loosely attached than in other Pinni- 
grades; 2, tail externally deficient from the greater development of the caudo-tibial 
membrane ; 3, a broad supraanal fold; 4, skin deeply and much wrinkled; 5, external 
} Hunterian Lecture, reported in ‘ Lancet,’ 28th April, 1866, p. 466, 
