544 DR. J. MURIE ON THE ANATOMY OF THE SEA-LION. 
tially united with the small deep portion of the masseter muscle. Its insertion is into 
the outer surface of the ascending process of the mandible for a great part of the con- 
cavity of that portion of the lower jaw. 
Masseter—Compared with the Hyznide and Felidee, the fleshy fibres composing the 
masseter are but moderately strong in the Sea-lion. In Man the mass of flesh and 
tendinous fibres denominated masseter is arranged in such a manner as to form two 
bundles of different dimensions, and disagreeing somewhat in direction. This partial 
division of the muscle also obtains in Otaria, but is not limited to the genus. 
Its superficial and first layer (fig. 15, Ma‘) (using the term for perspicuity and accu- 
racy of description) arises along the whole length of the zygomatic arch, and is some- 
what quadrangular. With fibres directed in a backward and downward direction, it is 
inserted into the outer surface of the mandible, from the root of the ascending ramus to 
the angle. The latter portion passes well behind the articulation of the jaws. 
The second or deep layer (fig. 16, 1/a*) appears as if a continuation of the fibres of 
the second or superficial portion of the temporal; but, although intimately united with 
this said portion, it is distinguished from it by arising in a tendinous manner from the 
posterior corner of the zygomatic arch, and is inserted upon the anterior surface of the 
ascending condyle and part of the outer surface of the ascending ramus. 
Digastric.—Immediately below and parallel with the lower border of the superficial 
layer of the masseter there is an uncommonly large, strong and digastric muscle, which 
is fleshy and without median tendon (J, fig. 15, and Di, Di*, fig. 24, Pl. LXXIT.). It 
arises from the inferior margin of the paramastoid. Continuing thence over the lower 
surface of the condyle and outside the descending angular process, it proceeds forwards, 
exterior to the inferior and narrow edge of the horizontal ramus, to within an inch of 
the symphysis menti. 
3. Muscular Layers of the Back and Neck. (Plates LXX., LXXI., LXXIL.) 
Trapezius.—W hile somewhat continuous as a whole, it is nevertheless clearly divisible 
into two portions. I shall describe them as such. 
The first and hindermost portion is very elongated in form (fig. 15, Zz‘). It is thin, 
muscular, and of moderate breadth. Posteriorly its fibres reach the fourth (last) rib ; and 
here they are narrow. ‘They become wider by degrees as they reach forwards towards 
the scapula, but contract again in a wedge-shape previous to their insertion into the 
upper portion of the scapular spine. 
The second and anterior part is, like the last, thin. In front it reaches the last 
cervical vertebra, and behind extends backwards to about the third or fourth dorsal 
spine. Its fibres converge, to be inserted into the anterior surface of the spine of the 
scapula for its whole length; and their direction is from behind forwards and from 
within outwards, much according to the position of the limb (Zz’). The second portion 
of the trapezius partially overlaps the anterior border of the first or hinder portion, and 
