440 DR. J. MURIE ON THE ANATOMY OF THE WALRUS. 
Superficial Layers, Throat-, and Thoracic Muscles. 
As regards the cephalo-humeral (woodcuts 2, 3, & 4, C.h.), it is very large, and reaches 
but does not overlap the trapezius. Its insertion is into the head of the humerus. A 
somewhat triangular pencil of fleshy fibres is continued as far as the middle of the 
humerus, near the deltoid ridge. This part may, indeed, represent a portion of the 
compound deltoid found in some animals. 
The sterno-mastoid in the Walrus has no semidivision as in the Sea-lion, but is 
clearly a single muscle and of moderate breadth. It arises sternally, as in the latter, 
but is inserted by a roundish tendon into the paramastoid in front of the levator clavi- 
cule. Between the attachment to the head of the sterno-mastoid and the anterior lower 
border of the cephalo-humeral, a portion of the omohyoid is seen to cross the neck. 
There is a long and ribbon-shaped muscle in close relation with the cephalo-humeral, 
which latter covers it until within a few inches of its insertion. With an origin from 
the paramastoid posteriorly, the muscle in question is inserted into a minute fibrous 
transverse band, which here represents a rudimentary fibrous clavicle, inasmuch as it 
lies opposite the shoulder-joint. 
Another distinct and separate, but also longitudinal, muscle arises by a tendon from 
the atlas, and proceeds to the spine of the scapula near the acromion process. 
The former of these two muscles just described may be regarded as the homologue of 
a cleido-mastoid, and the latter, although fixed to the scapula, be the representative of 
the so-called levator clavicule. Besides the last mentioned, a true levator anguli sca- 
pule is found, similar to what obtains in O. jubata. 
The trapezius is double (woodcut, fig. 3, 7z' & Tz’). The posterior portion corre- 
sponds with the condition found in Ofaria jubata; but the anterior differs in its 
running quite over the shoulder-joint, and being inserted by aponeurotic fascia into 
the neck of the humerus and deltoid ridge; as it glides over the shoulder it covers the 
small second division of the deltoid. Prof. Humphry’s remark", that the trapezius and 
deltoid in the common Seal may be regarded as one muscle, is in some senses not 
inapplicable in the case of the Walrus. 
As is the rule in Carnivora, the insertion of the latissimus dorsi, or that portion of it 
designated humero-dorsalis by Prof. Haughton’, is, with the panniculus carnosus and 
deep layer of the pectoralis, into the humerus. Its costal origin, as in the Otary, is 
from the hindmost seven ribs ; and it interdigitates with six slips of the rectus abdominis. 
The second portion of the grand dorsal (lombo-humérien), described by Duvernoy’, 
Humphry‘, and Haughton‘ in Phoca, and termed scapulo-costalis by the latter, is not 
so clearly separated in Trichechus. 
There is a serratus posticus anterior which is comparatively well developed, broad 
‘ Paper cited, p. 298. 
2 « Notes on Animal Mechanics—Muscular Anat. of Seal,” K. I. Acad. 23 May, 1864. 
* Mém. du Mus. d’Hist. Nat. t. 9. 1822, p. 60. * Loc. cit. p. 297. ® Loc. cit. p. 39. 
