180 Macieay Memoria Voiume. 
indeed pretty rapidly occurs in the unprotected skin of the snout. In the living, 
” 
perfectly fresh specimen the skin is not even “leathery” or “ pergameneous,” like that 
of the duck, but on the contrary is, as Waterhouse (5) described it, “naked skin”— 
“uniformly smooth and flexible’—not only at the free margins or lip-folds but 
throughout the whole extent of the muzzle. This integument is not even remarkably 
thick as the latter author’s description elsewhere implies, since the epidermal layer 
averages about 0-4mm. 
In the living animal the whole muzzle, including both upper and lower jaws, is 
covered by smooth soft and humid skin, pigmented over the whole dorsal aspect of 
the muzzle, but pale or almost white on the ventral aspect. Both on the upper and 
lower jaws the skin-covering extends beyond the limits of the osseous facial skeleton, 
forming free flexible upper and lower lips bounding the entire gape. 
These lips, however, do not consist of skin folds only, but, as will presently be 
seen, they possess a cartilaginous skeletal basis, and in this latter respect, certainly, 
they differ from true lip-folds. It will be convenient, however, to continue to refer to 
them as the lips of the animal. 
It is unnecessary to enter into any detailed description of the osseous skeleton 
of the jaws as the anatomy of the dried adult skull is adequately given in the various 
text-books which deal with the subject. But the cartilaginous basis of the lips 
forming a marginal extension of the skeleton of both upper and lower jaws is 
completely ignored by some writers, though noticed and figured by Meckel (6) and 
subsequently by Owen (7) and by W. K. Parker (8). The latter author, indeed, has 
fully recognised the importance of the arrangement in question, but we believe that 
its true significance in the morphology of the skull of the animal has been hitherto 
entirely overlooked, and indeed we are unaware that any author except Parker has 
inquired into the question. 
The skeletal basis of the upper lip forms a strip of cartilage, which averages 
about a centimetre in breadth, and is intimately adherent laterally and in front to the 
free margins of the maxillze and premaxille, which are slightly grooved for its better 
attachment. Its lateral part extends backwards as far as the lateral projection of the 
maxilla which overhangs the antorbital foramen and is attached to that process 
opposite the opening of the foramen, so that some of the nerve bundles issuing from 
it pass superior and some inferior to the cartilage, lying between it and the skin 
above and below to which they are distributed. 
The corresponding cartilage in the lower lip forms a somewhat similar strip 
attached to the anterior divergent ends of the rami of the mandible, but it has a 
more limited lateral and backward extension than that in connection with the upper 
jaw, while, as will presently be pointed out, it also differs structurally from the latter. 
