Art. XVIII.— Observations on the Ziphidæ, a Family of the Cetacea.
[Read before the Wellington Philosophical Society, January 29, 1870.]
Three specimens of this remarkable family have come under my notice:—
In January, 1862, a male specimen was embayed in the Porirua Harbour, and was captured by Mr. London, of which I was only able to make a rude sketch, and take a few of the measurements.
In January, 1866, a male specimen was stranded in Titai Bay, and was captured by Mr. H. Arthur. Of this specimen I was enabled to make a tolerably correct drawing (see Plate XIII., fig. 1), and, at the same time, obtained numerous portions, including the head now in the Museum.
In January, 1870, a specimen was stranded in Worser's Bay, near the entrance to Port Nicholson, and was captured. Of this specimen I obtained the entire head.
I will confine my remarks to the leading peculiarities of the Ziphidœ, namely, the presence or absence of teeth. It is admitted by naturalists, and more especially by Dr. Gray, of the British Museum, that the history of these animals is involved in the greatest uncertainty. There cannot be a doubt that a correct representation taken from life is of primary importance, but in the case of the Cetaceans, including animals of gigantic proportions and whose habitat is the ocean, a correct likeness can scarcely be obtained; and the very fact of reducing an animal a hundred feet in length to suit the dimensions of an octavo volume is liable to destroy every vestige of a true or correct idea, even in the mind of the matured and experienced philosopher.
These remarks apply more especially to the animals forming the subject of the present notice.
In the recent state no vestige of teeth can be discovered, and thus the term Aodon might and indeed would have been applied, even by practical or scientific naturalists, to such specimens. In the case of my first specimen no dissection was obtained, and I described it in a short notice, published in the local press, as a specimen of the Aodon. In my second specimen, in like manner, not a vestige of teeth could be seen, the snout perfectly resembling the beak of a bird; the blubber had been removed before I saw the animal, so that I was only able to procure the head and other portions of the skeleton. These were put into the macerating tub, and in due time the bones were picked out of the debris, when a remarkably shaped tooth (Plate XV., fig. 4b) was discovered close to the symphysis of the lower jaw. In my third specimen, in like manner, no appearance of teeth (although
anxiously looked for) could be detected, but upon a careful dissection, and previous to maceration, the tooth (Plate XVII., fig. 3b) now before the Society was found; its twin brother still remains in its obscurity on the right ramus of the lower jaw.
From the appearance of the teeth, I am inclined to think that they never cut or appear above the gum, and the scientific enquirer will naturally ask of what use could they be to the animal? This is truly a profound question, and carries us into the mysteries of types and first causes. The tooth, it will be observed, is of the form of a compressed cone; the apex is finely pointed (not worn), and was found playing in a cavity, resembling a socket, in the jaw. The tooth is still covered to within about the eighth of an inch with an investure of cartilaginous tissue, but as I intend to carry out my investigation of not only this remarkable tooth, but also those of other Cetaceans, including the teeth of the sperm whale, I shall close my present remarks by stating, that from careful examination of the specimens which came under my notice, the food on which these animals subsist is the cuttle-fish; and these concealed teeth, although not answering the purpose of securing, killing, or grinding, would yet give a severe pinch to such soft-bodied animals.
I subjoin tables of weights and measurements so far as could be procured:—
|Tail, from tip to tip||7||0|
|Head—length of basal surface||4||4|
|" breadth across occiput||2||0|
|" length of lower jaw||3||10|
|Length of pectoral extremity, free||3||0|
Produce of fine sperm oil, about 240 gallons; spermaceti, a considerable quantity on the upper surface of the face.
|Head—from tip of jaw to nostrils||1||5|
|" " eye||1||5|
|" " gape||0||9|
|Head—total length of basal surface||2||0|
|" " breadth||1||0|
|" " height||1||0|
|From beak to nostrils||3||6|
|" " nostrils to occipital foramen||1||6|
|Total length over vertex||5||0|
|Head—tip of beak to occipital foramen, basal surface||4||0|
|" " greatest height||2||0|
|" " length of lower jaw||3||10|
|" " " " symphysis||1||0|
|Breadth between condyles||1||10|
|" " at symphysis||0||6|
[Read before the Wellington Philosophical Society, June 25, 1870.]
Since reading the preceding notice, I have made a section of the left tooth, as nearly in its axis as the curves of the tooth would allow, and without injuring the apex. It will be observed from this section that there is no cavity for lodging a pulp; it is composed of three distinct substances, well defined, not only by difference in colour but in organization, but just of sufficient hardness to take a fine polish; the centre part, forming much the greater proportion of the tooth, exhibits a homogeneous mass of fibres edged with a series of imbricated laminæ, more especially towards the apex, and these are covered with a white dense osseous tissue, precisely similar to the ivory or bone of the tooth of the sperm whale, of which I also have placed on the table a fine section. Lastly, enamelling the tooth from the base to within an eighth part of an inch of the apex, we have an osseous layer, not only holding the place of the enamel in other teeth, but presenting its peculiar and characteristic organization; the section, at the same time, shows the last mentioned tissue to be entirely covered by a substance similar to cartilage, as if it was in a state of growth by the deposit of enamelling matter.
The muscles chiefly performing the process of mastication are comparatively small, and would scarcely serve the purpose of seizing, killing, and grinding any resisting prey.
It is sufficiently interesting to remark that the Delphinidœ are characterized by the great number of teeth, some of them possessing as many as two hundred, whilst the Ziphidœ, the skeleton of which closely resembles the dolphin, may
be said to be toothless. Indeed, a careful anatomical examination of the lower jaw of the animal I am now describing, presents appearances strongly suggestive of the presence in the fœtus of numerous teeth. The canal for the dental nerve is remarkably large, and I experienced considerable difficulty in extracting a mass composed of large nervous filaments and blood vessels, evidently transmitting branches to, if not teeth, at least to the alveole and its living membrane or gum. Had the development of these supposed fœtal teeth been completed, the Cetacean under examination would have been a sperm whale, a Cachalot in short. The dissection of a fœtal mystecetus, made by myself, showed the existence of numerous teeth in both jaws; although at or before the birth of the animal, the development of these teeth is checked, and the nerves and nourishing vessels are appropriated to the development of baleen.
A question arises, is the specimen under consideration an adult animal? and, would these teeth be ultimately protruded? The present state of the question, as clearly indicated in Dr. Gray's eighth family of the Cetaceœ, would lead us to conclude that the tooth was a rudimentary affair; but I answer, its high organization, as shown in the section, leads me to question this view.
Notes on the Preparations mentioned in the foregoing Paper.
The three Whales described by Dr. Knox in the foregoing paper, are evidently to be classed with the Family Ziphidœ, as defined in Dr. Gray's Catalogue of Seals and Whales, p. 326.
Plate XIV. gives three views of the skull (two feet in length) of the young specimen that was captured in Porirua Harbour, in 1866, the dimensions of which have already been given (Trans., Vol. ii., p. 27.).
Figure 1 is the side view without the lower jaw, Figure 2 shows the upper surface, and Figure 3 the lower surface of the same. The curious obliquity of the skull, which twists forwards and upwards to right half of it, as shown in the drawing, especially by the relative position of the two segments of the blow-hole, is matter of remark, as it is found to exist in all the specimens of whales and their allies yet examined, and probably corelates with some modification of the progress of the animal through the water, to enable it to enjoy direct forward vision.
Plate XV. gives three views of the lower jaw belonging to the same head. In Figures 1 and 3, which are the profile and inferior views, it will be observed
that there are three nutrient canals at the tip of the jaw on each side, probably indicating the normal number of teeth. In Figure 2, which shows the upper surface of the jaw, there is only one socket on each side (a and á), which held the tooth figured of natural size (4a and 4b.) The upper conical part of this tooth has a polished surface, but never protrudes through the gum.
This is well shown in Figures 5a and 5b, the first of which shows the left side of the top of the jaw, with the integuments still in place, the position of the tooth being only revealed by a slight elevation without any aperture. The second shows the opposite side of the jaw with the integuments removed, and the tooth which came away imbedded in a fold of the gum, dissected out and replaced in the socket.
Plate XVI. gives the superior, inferior, and profile views of the skull of the third specimen referred to by Dr. Knox; the dimensions of which are as follow:—
|Length of head||59.5|
|" dental groove||15.0|
|" lower jaw||43.0|
|Width of notch||14.5|
|" at orbits||24.5|
|Height of occiput||19.5|
Plate XVII. gives the corresponding view of the lower jaw (Figures 1 and 2), and also the tooth (Figures 3a and 3b), both in side view and in section, showing the internal structure. The form of the tooth is more turned than in the other specimen, but the variety is probably due to age.
The preparation of the nose (Figures 4a and 4b), show that notwithstanding this is a full-sized animal, the tooth is still sheathed in the gum, being imbedded in a tough cartilaginous sac, which adheres loosely in the socket of the jaw, and is moved by a series of muscular bundles that elevate and depress it.