224 MR. R. OWEN ON THE YOUNG OF 
The situation of the exterior nostrils has already been given ; they communicate with 
the mouth by the foramina incisiva, which are situated at nearly 3 lines’ distance from 
the end of the upper mandible, and are each guarded by a membranous fold extending 
from their anterior margin: the nasal cavity then extends backwards, and terminates 
immediately above the larynz, the tip of the epiglottis'! extending into it, and resting 
upon the soft palate. 
On the middle line of the upper mandible, and a little anterior to the nostrils, there 
is a minute fleshy eminence lodged in a slight depression. In the smaller specimen 
this is surrounded by a discontinuous margin of the epidermis, with which substance, 
therefore, and probably (from the circumstance of its being shed) thickened or horny, 
the caruncle had been covered. It is a structure of which the upper mandible of the 
adult presents no trace, and is obviously analogous to the horny knob which is observed 
on the upper mandible in the foetus of some Birds. I do not, however, conceive that 
this structure is necessarily indicative of the mandible’s having been applied, under the 
same circumstances, to overcome a resistance of precisely the same kind as that for 
which it is designed in the young Birds which possess it. The shell-breaking knob is 
found in only a part of the class; and although the similar caruncle in the Ornitho- 
rhynchus affords a curious additional affinity to the Aves, yet as all the known history 
of the ovwm points strongly to its ovoviviparous development, the balance of evidence 
is still in favour of this theory. 
The situation of the eyes was indicated by the convergence of a few wrinkles to one 
point ; but when, even in the larger of the two specimens, these were put upon the 
stretch, the integument was found entire, and completely shrouding or covering the 
eyeball anteriorly. This fact is one of great importance to the question of the mam- 
miferous character of the Ornithorhynchus. For on the supposition of the young animal 
possessing locomotive faculties, which would enable it, like the young Gosling, imme- 
diately after birth or exclusion, to follow the parent into the water, and there to receive 
its nutriment (whether mucous or otherwise), the sense of vision ought certainly to be 
granted to it in order to direct its movements. The privation of this sense, on the 
contrary, implies a confinement to the nest, and a reception on land of the mammary 
secretion of the parent. 
The general form of the body, and the cartilaginous condition of the bones of the 
extremities, equally militate against the young Ornithorhynchus possessing at this period 
of its existence active powers of swimming or creeping. The head and tail are closely 
approximated on the ventral aspect, requiring force to pull the body out into a straight 
line; and the relative quantity of integument on the back and belly shows that the 
position necessary for the due progressive motions is unnatural at this stage of growth. 
The form of the young Kangaroo soon after birth is very similar to this, which is com- 
mon to the foetus both of the viviparous and oviparous classes. 
! The epiglottis is essentially associated with lactation, not with viviparous generation. 
