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Show 286 PROF. HUXLEY ON THE CRANIAL AND [Apr. 6, Icticyon and Paleeocyon. The heel of this tooth also diminishes in proportion to its blade. IV. All the known kinds of canine animals may be arranged in two series, starting from Otocyon as the nearest ally of the lowest member of each series. It is probable that when a sufficient number of specimens of each species at present recognized has been examined, it will be found that the forms with least-modified skulls and teeth are connected by insensible gradations with those with most-modified skulls and teeth, and that no absolute line of demarcation can he drawn between one species and another in cranial and dental characters. There is no evidence that any one of these species is infertile when crossed with any other. Such evidence as exists with respect to C. cancrivorus, the Jackal, Dog, and Wolf tends to the conclusion that species of approximately the same size are capable of fertile unions. V. The taxonomy of the Canidae, under these circumstances, is very much a matter of convention. I am disposed to think that the most convenient mode of representing the facts is to regard Otocyon and the Thooid and Alopecoid series respectively as genera, retaining for the two latter the old names of Canis and Vulpes. In each of these genera a lower, a middle, and a higher section may be conveniently recognized, though they are hardly susceptible of strict definition. Thus, in the genus Vulpes, Baird has separated V. littoralis and V. einereo-argentatus under the name of TJrocyon. The Corsacine Foxes, V. zerda, V. caama, V. bengalensis, and V. velox may constitute another subgeneric section, and the most differentiated Foxes, such as V. lagopus, V. fulvus, and the rest, a third. In the genus Canis we have, in like manner, as a lowest section the species of the C. cancrivorus and C. vetulus type (answering pretty much to the Aguarra Dogs of Hamilton Smith), the Sacaline section (C. aureus, C. anthus, C. mesomelas, G. antarcticus, G. latrans), and the Lupine section (C. lupus and all its varieties). Icticyon, Lycaon, and Cyon may probably be usefully retained as subgeneric names for the special modifications of the Thooid type which are denoted by them. As for species, no one zoologist has ever yet agreed with the estimate of another as to what should be considered species and what local varieties among Wolves and Foxes ; and, as there is no criterion by which the question can be decided, it is probable that such agreement never will be attained. The suggestion that it may be as well to give up the attempt to define species, and to content oneself with recording the varieties of pelage and stature which accompany a definable type of skeletal and dental structure in the geographical district in which the latter is indigenous, may be regarded as revolutionary ; but I am inclined to think that sooner or later we shall have to adopt it. VI. The most notable facts in the Distribution of the Canidae are:- (I) the occurrence of the Corsacine Alopecoids and the Sacaline |
