■Cetacea. 
Cetacea.- 
-MAMMALIA.- 
-Cetacea. 
193 
Two or three more species have been described. Of 
these may be mentioned, Smith’s Hyrax {Ilyrax 
arhoreiis) from South Africa; this form possessing 
arboreal habits, and being distinguished by its longer 
fur, which also displays a white spot on the back. 
Another species, capable of climbing trees and feeding 
on their fruits, is the Hyrax Sylvestris of Temminck. 
This form inhabits New Guinea and other parts on the 
west coast of Africa, and it is remarkable as possessing 
only twenty-four grinding teeth ; that is, three pre- 
molars and three true molars on each side of either 
jaw, the orbital ring being at the same time more 
complete than obtains in any other member of the 
family. 
Order XII.— CETACEA. 
Although scientific naturalists have uniformly insisted 
on the mammiferous character of the cetacea — at least 
since the days of Cuvier, and also, in some degree, 
from the time of Linnaeus — the majority of 
people still class them with fishes; but the only 
grounds on which these animals can with any 
propriety be said to resemble the finny tribe, 
are those which refer to their form and the 
conversion of the anterior limbs into finlike 
paddles. Even here, however, a close inspec- 
tion of the leathery hide, of the modified limbs, 
and of the horizontal tail, is sufficient to indicate 
a wide departure from the fishes properly so 
called, in which the tail is vertical, the fins 
composed of numerous rays, and the integu- 
ments more or less converted into separable 
scales; and what is still more distinctive, we 
also find conspicuous indications of the repro- 
ductive organs externally, as well as mammary 
glands in the female. Anatomical investi- 
gation has likewise shown that these gigantic denizens 
of the deep breathe by means of lungs, and that 
they have a pulmonic and systemic circulation, as 
obtains in other mammals. Taking the skeleton of 
the common Greenland whale — Plate 32, fig. 90 — as a 
type of zoophagous cetacea, it is extremely interesting 
to observe how its several osseous elements have 
become modified in form, and altered in bulk, in order 
to meet the exigencies of a creature destined to live in a 
medium so different from that generally enjoyed by the 
mass of mammalian vertebrates. Commencing with 
the head, the first thing that strikes us is the remark- 
able extension of the bones of the face, the inter-max- 
illary and superior maxillary bones arching forwards to 
form a kind of rostrum, whilst the lateral divisions of 
the lower jaw converge towards the tip of the snout, 
forming a curve on either side scarcely less conspicuous. 
The cranial bones are not less altered ; the nasals are 
short, the temporals square-shaped, the frontals remark- 
ably narrowed and directed obliquel}'’ outwards and 
backwards, the vertex of the skull being almost entirely 
occupied by the upper flattened portion of the occipital 
bone. All these characters are well displayed in the 
accompanying woodcut (fig. 7G). If our attention be 
next directed to the vertebral column, we find on the 
one hand an almost complete abrogation of the cervical 
region, and a striking augmentation of the caudal ele- 
ments on the other; taken as a whole, however, the 
bone-chain is massive and well developed. The most 
interesting feature in connection with this part of the 
VoL. I 2.5 
skeleton has reference to fehe vertebrae of the neck, 
which in all cases maintain their typical number, 
althmigh, in the true whales, they are completely ossified 
Skull of the Gveenlind Whale (Balscna Mysticeliis), 
seen from above. 
together so as to form a single mass, more or less 
fissured by deep clefts, which serve to indicate the 
original existence of seven distinct vertobrse in the 
embryonic condition. But this is only true of the 
whalebone whales, for in other members of the ordei 
the several segments are more or less free, there being 
six anchylosed together in the spermaceti, and two 
only in the piked-whales, the dolphins, and the por- 
poises; in the latter the first and second vertebrae are 
conjoined; but in the Balanopterae the union takes 
place between the second and third cervical segments. 
In the herbivorous cetacea all the bones are perma- 
nently free, and this is also the case in the sou-sou or 
dolphin of the Ganges. In regard to the dorsal and 
lumbar vertebrae, all that we need remark is, that both 
series vary in number, in different genera, while their 
spinous and transverse processes become more and 
more conspicuous as they approach the caudal series. 
One, two, or three vertebrae have been assigned to the 
sacral or pelvic region, but these do not differ in 
structure from the previous group ; and but for the 
existence of rudimentary pelvic bones, it would be 
scarcely fair to say that any should be classed in this 
category. The vertebrae of the tail are extremely 
numerous, upwards of thirty being present in the 
Rorqual ; structurally they vary quantitively and mor- 
phologically, gradually diminishing in bulk and com- 
plexity of outline from before backwards, until we 
ultimately find them reduced to a simple compressed 
nodule at the free extremity of the organ. Of the rudi- 
Fig. 76. 
