In the young animal described by Mr. Bennett, (which in weight was probably not more than one-third of that of the present animal) the hairs of the body are of an uniform deep brown colour; hence, if I am right in considering Mr. Darwin’s animal as the same species, it would appear that the grizzled character of the fur is dependent on age.
The semi-erect fur will also serve to distinguish the present species from the Lutra Platensis; the fur is likewise longer, the tail is shorter, and the feet are smaller in proportion. The most important distinctions, however, are furnished by the skulls; I will, therefore, compare them.
The skull of L. Chilensis compared with that of L. Platensis, (Plate 35, figs. 4.) when viewed from above, presents but little difference in general form; it is, however, smaller in all its proportions, and the zygomatic arch is a little less convex: the palate is proportionately shorter; the tympanic bullæ are much smaller, less elevated, and wider apart, in which respect there is a greater approximation to the skull of L. vulgaris than to that of L. Platensis; but here, the tympanic bullæ are larger than in L. Chilensis. Both in L. Chilensis and Platensis, the sub-orbital foramina are kidney-shaped, the emarginated portion being downwards, whilst in L. vulgaris they approach somewhat to a triangular figure, the apex being external. In L. Chilensis, however, this foramen is comparatively larger than in L. Platensis, and the outer portion of the foramen forms the segment of a larger circle than the inner one, whilst in L. Platensis both portions are equal.
The principal difference in the dentition of the La Plata and the Chile otters, consists in the comparatively smaller size of the posterior molars, both of the upper and lower jaws, of the latter species. In the upper jaw, the “carnassière” has its inner lobe, approaching somewhat to a triangular form, whereas in L. Platensis it is broader and almost semicircular. In the lower jaw, the last molar but one has the inner lobe much smaller than the middle outer lobe, whilst in L. Platensis these two lobes are of nearly equal size and elevation. Other points of dissimilarity will be perceived in the annexed table of admeasurements.
| L. Chilensis. | L. Platensis. | ||||
|---|---|---|---|---|---|
| In. | Lines. | In. | Lines. | ||
| Whole length of skull | 3 | 9¾ | 4 | 2½ | |
| Greatest width | 2 | 6⅓ | 2 | 10⅓ | |
| Width of skull from the apex of one mastoid process to the opposite | 2 | 3¼ | 2 | 8¼ | |
| Length of palate | 1 | 6 | 1 | 10 | |
| Breadth of palate between the posterior molars | 7¾ | 7¾ | |||
| Length | from last molar to posterior margin of palate | 3⅓ | 5½ | ||
| from base of canine to hinder part of last molar | 11⅔ | 1 | 1⅓ | ||
| of carnassière | 5 | 5⅔ | |||
| Width of do. | 5 | 6¼ | |||
| Length of last molar | 2¾ | 3½ | |||
| Width of do. | 4⅓ | 5⅔ | |||
| Length | of ramus of lower jaw | 2 | 4½ | 2 | 8¾ |
| from canine to hinder portion of last molar (lower jaw) | 1 | 2¼ | 1 | 4¼ | |
| of last molar but one (lower jaw) | 5¾ | 6⅔ | |||
| Width of do. | 2⅔ | 3½ | |||
“These animals are exceedingly common amongst the innumerable channels and bays, which form the Chonos Archipelago. They may generally be seen quietly swimming, with their heads just out of water, amidst the great entangled beds of kelp, which abound on this coast. They burrow in the ground, within the forest, just above the rocky shore, and I was told, that they sometimes roam about the woods. This otter does not, by any means, live exclusively on fish. One was shot whilst running to its hole with a large volute-shell in its mouth; another (I believe the same species) was seen in Tierra del Fuego devouring a cuttle fish. But in the Chonos Archipelago, perhaps the chief food of this animal, as well as of the immense herds of great seals, and flocks of terns and cormorants, is a red coloured crab (belonging to the family Macrouri) of the size of a prawn, which swims near the surface in such dense bodies, that the water appears of a red colour. This specimen weighed nine pounds and a half.”—D.
Family-DELPHINIDÆ.
Delphinus Fitz-Royi.
Plate X.
D. suprà niger; capitis corporisque lateribus, corporeque subtùs niveis; caudâ, pedibus, labioque inferiore, nigris; fasciis latis duabus per latus utrumque obliquè excurrentibus, nigréscenti-cinereis, hujusque coloris fasciâ, utrinque ab angulo oris ad pedem tendente.
Description.—Upper parts of the body black, under parts pure white, the two blended into each other by gray: extremity of snout, a ring round the eye, the edge of the under lip, and the tail fin, black; dorsal and pectoral fins dark gray; a broad gray mark extends from the angle of the mouth to the pectoral fin; above which, the white runs through the eye and is blended into gray over the eye; two broad deep gray bands are extended in an oblique manner along each side of the body, running from the back downwards and backwards; iris of eye dark brown. Body anteriorly somewhat depressed, posteriorly compressed; head conical, arched above; the lower lip projecting beyond the upper; eye placed above and behind, but near the angle of the mouth; breathing vent situated in the same line as the eyes—supposing a circle to be taken round the head. Teeth slightly curved, and conical; in the upper jaw twenty-eight in number on each side, and in the lower, twenty-seven.