450 DR. J. MURIE ON THE ANATOMY OF THE WALRUS. 
disagree with the condition extant in the Sea-lion. A superficial and a deep layer are 
not so well defined in the Walrus. There is a single interosseous belly to the fifth 
digit on its radial side, and also a single larger muscle to the first digit on its ulnar 
side; the second, third, and fourth digits have each moderately developed double 
interossel. 
Interossei of manus, with portion of antibrachial bones, to 
display the pronator quadratus muscle. 
P.q. Pronator quadratus, F.c.r. Tendon of the flexor carpi 
radialis. -A.m.d. Abductor minimi digiti. Op.p. Oppo- 
nens pollicis, J', J, 7%, J+, 1°. The double or deep 
interossei. Sz’. Superior interosseous muscle. J, IJ, 
III, IV. V. Applicable to the respective shortened 
digits. 
The representatives of a superficial layer are two in number, one of which, however, 
may, indeed, be the representative of the abductor minimi digiti. This latter, long and 
thin, arises on the surface of the deep palmar fascia and ligamentous interosseous union 
at the base of the third phalanx. Crossing obliquely outwards, its insertion, chiefly 
fleshy, is into the binding fascia on the radial side of the distal end of the fifth meta- 
carpal in common with the single interosseous muscle. The second of the superficial 
layers has a position identical with the last, but slightly to its radial side, and it is 
inserted into the fourth digit. 
Muscles of the Abdomen, Loins, and Tail. 
In the Walrus the digitations of the external oblique are carried forward to the 
fourth rib, and four slips of the serratus magnus interdigitate with it, besides six or 
seven of the latissimus dorsi behind that. 
The diaphragm is very strong and almost entirely muscular. The central tendon 
differs somewhat in shape from that in Otaria, inasmuch as the median portion is broader 
and rounder. The diaphragm has an attachment to the ensiform or xipho-cartilage, and 
laterally extends to the tenth and ninth sternal ribs or rib-cartilages; thence it passes 
backwards to the remainder of the ribs, inclining inwards to the tip of the transverse 
process of the first lumbar vertebra (where it is fleshy), and with fibrous tissue fixes 
itself to the bodies of the second and third lumbar vertebra. It likewise sends a small 
tendon which is inserted into the body of the fourth lumbar vertebra. 
Psoas muscles—There appears to be a partial division between the psoas parvus and 
