542 DR. J. MURIE ON THE ANATOMY OF THE SEA-LION. 
tense, and slightly lend aid when the head is bent backwards. ‘The superficial muscular 
fibres on the ventral aspect of the neck and cheeks are apparently too sparse and weak 
to assist much in flexion of the head; their office seems rather to be corrugators of the 
skin and subcutaneous tissues. 
2. The Cranial Muscles. (Plate LXX.) 
An occipito-frontalis (P1. LXIX. fig. 14, o,f) does exist, but it cannot be said to be fully 
developed; it is so mingled with the carneous fibres of the platysma, and particularly 
with the nuchal portion of the very extensive fleshy panniculus behind, that its limits 
are with difficulty defined. There is, however, a tolerably thickish muscular part upon 
the forehead and between the orbits. This merges into aponeurotic fascia as it passes 
on towards the nasal region. 
Of facial layers the orbicularis palpebrarum presents a considerable broad and thick 
circuit of muscular fibres round the orbit (fig. 15, 0.p), and is inserted into the tendo 
oculi and superior maxillary bone. 
The nasal region is covered superficially by a thick fleshy expanse, which is fixed to 
the upper portions of the maxillary and premaxillary bones, and sweeps forwards the 
entire length of the fleshy muzzle. This massive layer constitutes the levator labii 
superioris aleque nasi (L.1.s.a.n, figs. 15 & 16). 
Beneath the last is a second muscular sheet, equivalent to the levator labii superioris 
proprius (L.s.p). It springs from the upper maxillary limb and fore part of the orbital 
circuit, and is inserted along the anterior part of the maxillary and premaxillary bone, 
a little way above the alveolus, from opposite the premolars to the incisors. 
A third, more deeply situated muscle I take to be the levator anguli oris (L.a.o). It 
is much smaller than the two preceding, and, unlike them, is broadest above and tendi- 
nous below. Origin, from the upper apex of the premaxilla and from the adjoining 
maxilla, resting mainly on the latter bone; insertion, the canine fossa, being overlain 
by the infraorbital nerves and depressor nasi muscle. 
Almost continuous with the fore part of the levator, fleshy fibres cover the nasal 
cartilages, and, whilst meeting their fellows of the opposite side above, run down laterally 
and partly mingle with those of the levator superioris proprius and depressor ale nasi, 
besides being in part fixed to the premaxilla. Situation and function show the muscle 
in question (C.n) to be homologous with the compressor naris of Man. 
The dilatator naris (D.n), or what in human anatomy goes also by the name of the 
levator proprius ale nasi posterior, is in Otaria an immensely developed and elongate 
muscle. Besides partially springing by fibre attached to the inferior lateral aspect of 
the premaxilla and nasal cartilage in front of the levator anguli oris, the dilatator arises 
in common with the depressor, presently to be spoken of, from the maxillary, anterior 
to the infraorbital foramen. Diverging therefrom, the dilatator passes upwards and 
forwards, crossing the great mass of the infraorbital nerves and vessels (Zn), and, super- 
