508 DR. J. MURIE ON THE ANATOMY OF THE SEA-LION. 
derance. It occupies about half the total length, the other half being divided betwixt 
the orbital region and the face proper or maxillo-premaxillary parts. The entire skull 
is low, broad, and flat on the top. Superiorly, from occiput to nasals, approaches an 
equal-sided triangle. The breadth of the mid frontals is not only relatively but abso- 
lutely a trifle greater than in the aged animal. On the other hand, the prefrontal pro- 
cesses scarcely extrude. The jugals have but slight arching. The occiput is altogether 
full, flat, and vertical; the condyles project little. Premaxille comparatively short and 
high ; spheno-orbital vacuity shallow, height proportionally great to length. Palate 
shallow and short. Basioccipital and sphenoid parts smooth, and all other processes 
small. Mandible with shallow shelving symphysis; a wide ramal arch; condyle short- 
necked and low-set. 
Second stage. In this cranium, authenticated as a yearling, there is a sensible change 
of cerebral to facial and prefrontal areas. Maxille and premaxille begin to lengthen. 
Mid frontals narrow relatively to increase of prefrontal processes. The brain-region 
becomes somewhat quadrangular; occiput rougher and begins to shoot backwards. 
Temporal groove deepens; jugal arch increases. ‘The permanent teeth in place give 
more character to the mouth; lengthening and deepening of palate obvious; the 
hamular processes approach. Eminences of spheno-occipital and other regions show 
indications of growth, but are not prominent. Condyles and coronoid processes of 
lower jaw exhibit a tendency to vertical elevation; mental portion of symphysis inclined 
to become tuberose. 
Third stage. Face, orbito-frontal, and brain-division now bear more equal propor- 
tion; that is, the two former have increased in a greater ratio than the latter. The 
mid frontals appear more scooped by reason of prefrontal development. By elongation 
of condyles and concomitant increase of basi- and exoccipitals, the occiput acquires a 
reverse obliquity to the first stage. The outline of the brain-cavity remains in abeyance, 
whilst temporal and occipital crests become apparent, though yet moderate. Mastoid 
and preoccipital eminences acquire a certain prominence. Orbito-jugal arch wider; 
premaxille decidedly elongate. Teeth, especially canines, enlarged. Palatal grooving 
deepened, the pterygoid processes nearing, hence postnares less open. Muscular im- 
pressions on basioccipital well scooped, basiocciput turning upwards behind. Symphysis 
lengthened ; upward tilt of ascending ramus. In this stage sexual distinction becomes 
evident, although there is still considerable resemblance between them. 
Fourth stage. Here the changes become very notable. The excessive growth of the 
canines of the male produce rounder, fuller premaxille. Brain-expansion is arrested. 
Mid-frontal width retrogrades, while prefrontal progresses. ‘The jugal arch expands, 
its orbital segment deepens, its post upper angle rises; the maxillary surface of orbit 
gets fuller. Parieto-occipital crests and processes acquire importance; and this causes 
the after part of the top of the skull to be elevated and no longer smooth and broad. 
Moreover on each side, at the fronto-parietal suture, bony projections appear. Arching 
