DR. J. MURIE ON THE ANATOMY OF THE WALRUS. 435 
be understood that I shall only specify deviations, describe afresh points obscure in 
Otaria, or state the parts unexamined; otherwise agreement is implied. Incidentally I 
may refer to muscular distribution in the Seal (Phoca); but throughout I purposely 
avoid a full comparison of the three forms in question. 
1. Muscles of the Skin, Cranium, and Spine. 
Equally as in the common Seal and Sea-lion, the panniculus carnosus in the Walrus is 
most extensively developed, but in the latter it has the coarsest fibres. There is a broad 
portion covering the buttocks, an ample layer on the sides of the body and abdomen, 
and, lastly, the shoulder-fibres lie over the deltoid and trapezius even in greater quantity 
than in Ofaria. 
Of the cutaneous fleshy layer representing the platysma, this is dispersed on the neck 
of the Walrus more abundantly than in the Eared or Earless Seals. 
The rather increased development of the dermal muscle of the shoulders and neck in 
the Walrus seems in harmony with the looseness of the skin and its greater flexibility 
in those regions in this animal. In OQ. jubata the part which covers the hips is uncom- 
monly strong; and accordingly it is in this creature that the more springy action of the 
sacral regions takes place, in the hobbling canter which it occasionally performs. But 
doubtless the youthful stage of the Trichechus, and consequent imperfect development 
or laxity of the muscular tissues, stood in the way of the latter tucking forwards its hind 
quarters so nimbly. In the Walrus, however, the continuation of the abdominal fibres 
by fascia into the groin, and their membranous extension towards the anal fold, the 
distal end of the tibia, and to the heel, are excessively coarse and thick. This disposi- 
tion of the superficial tissues or aponeurotic layer of the groin and caudo-tibial region 
appears at least to serve a twofold purpose—namely, connect the retractile efforts of the 
abdominal parietes with those of the semifixed lower leg, and defend the testicle from 
injury, as it lies upon the surface of the gracilis and semitendinosus muscles. 
As might be anticipated from the enormous muzzle and exceeding flexibility of the 
vibrissee or, rather, stout bristles inserted into the upper lip, the facial muscles, as a 
whole, are proportionally vast. They, indeed, form a fleshy mass of extraordinary thick- 
ness and great strength, separable, as in Otaria and Phoca, into several well-defined 
layers, which as a group chiefly play upon the nostrils and upper lip. In T’richechus, 
moreover, the number and magnitude of the infraorbital and facial nerves agree with 
the wonderful motor and semitactile power displayed in the structures to which they 
are disseminated. 
The size and force appertaining to the narial muscular group are most unusual, and 
far surpass those of most short-snouted mammals other than the Seals, excepting, it 
may be, the large aquatic Hippopotamus. In the living Walrus, which I had many 
opportunities of watching, it was curious to observe the manner of closure and dilatation 
of the nares. In coming out of the water, or under other circumstances where a full 
VOL. VII.—ParRT vi. June, 1871. 3P 
