ORCADENSIS 455 
are greatly enlarged (Fig. 72 and dimensions 8, 9, and 9-8 of 
table at p. 462). 
The pleistocene M7. corner? occupies a somewhat central 
position between J7/. sarnius and MW. orcadensis, but it is on 
the whole, as might have been expected, more primitive than 
either. The incisors are straightened and protruding, the 
cheek-teeth of normal avva/zs pattern, but light and short; the 
short nasals terminate roundly behind, the diastema is long, the 
posterior palatal septum grooved. The zygomata are narrow, 
the jugals heavy with boldly convex upper borders. The 
brain-case is long and narrow, the occiput intermediate in depth 
between 0. orcadensis and o. sandayensis, the temporal ridges 
fuse into a low but sharp inter-orbital crest, the post-orbital 
crest of the squamosals is weak, though long, the inter-parietal, 
coronal suture and posterior frontal processes are entirely 
unmodified in the adult, retaining to the full the form seen in 
young orcadensis ; anteriorly, however, the squamosals encroach 
upon the frontals, the distance between the right and left bones 
being no greater in adults than in adult 0. ovcadenszs. 
The Guernsey JZ. sarnius has an external appearance which 
recalls 17. agrestzs. In its cranium it is more specialised than 
M. cornert, except only in one respect, the wide anterior 
separation of the squamosals. The rather short nasals are 
cleft behind; the median septum of the hinder palate has no 
ventral groove. 
M. orcadensis stands considerably higher than either J7. 
cornert or M, sarnius. Owing to the richness of colour and 
length of the fur, the external appearance of its less modified 
southern sub-species is not very different from that of some of 
the Hebridean forms of agresézs ; in its northern races, westre 
and sandayensts, the colours tend to become pallid. The 
temporal muscles are throughout considerably stronger than in 
either of its allies, and in the transition from youth to age exert 
a much more powerful influence upon the form of the skull. 
In rvonaldshaiensts and orcadensts the posterior portions of the 
muscles appear to be more powerful than the anterior; 
accordingly in these forms the modification of the inter-parietal 
is more profound (in adults) than elsewhere. The post-orbital 
crests are relatively weak, the occiput deep. The upper borders 
