OCR Text |
Show 1880.] DENTAL CHARACTERS OF THE CANID.E. 239 number in Otocyon, and to the diminution of the number in Cyon and Icticyon. The variation in size of the pollex and its disappearance in Lycaon are well known. The differences in the form of the pupil have been noted ; and, of late, particular notice has been taken of the extensive modifications in the form of the caecum. Weight has been attached to the presence or absence of a caudal gland. The taxonomic value of these variations, however, has remained doubtful. That of the proportional lengths of the nasal bones, for example, is justly disputed by Wagner \ Satisfactory evidence of the form of the pupil is hard to obtain, and does not appear to have any definite correlation with diurnal or nocturnal habits. The presence or absence of a caudal gland has been investigated in only a few species ; and as it occurs in Wolves, Dogs, Jackals2, and Foxes, it is not likely to be of much importance. The proportions of the sectorial to the following teeth may be similar in Canidse which are certainly not closely allied, and different in those which are. And the system of measurement hitherto usually adopted gives the absolute sizes of the teeth and their dimensions relatively to one another, but affords no clue to their proportions in relation to the size of the skull, or to the increase or diminution of individual teeth. The increase of the number of the teeth of Otocyon appears generally to be regarded merely as an anomaly. There can be no doubt that the skulls and the teeth of the Canidae vary from species to species more than any other part of their organization. One has only to put side by side with one another the skeleton of an Otocyon and that of a Wolf or that of a Fox, to see that the cranial and dental differences are very much greater than any which are observable elsewhere ; and a glance at the skull and teeth of any other canine animal is sufficient to show that its characters give it a place somewhere between the former and the two latter. The problem therefore is how to give definite expression to the differences between Otocyon, Fox, and Wolf, and to determine by something better than vague eye-judgments the relation of the other forms to these. 2. W h e n occupied with anthropological questions, a good many years ago3, I was confronted by the same kind of difficulty in endeavouring to arrive at an exact conception of the morphological relations of the skulls of the different races of mankind ; and I was led to adopt a method of estimating cranial characters which still commends itself to m e as that which is best calculated to meet the end in view. Every constituent of the skull, like all other parts of the body, varies from individual to individual, and from youth to age. But the central region of the base of the skull, formed by the basioccipital, basisphenoid, and praesphenoid bones, represents the foun- 1 Schreber's Saugethiere, Suppl. Bd. ii. pp. 365, 384, notes. 2 I have found a small caudal gland in a female C. mesomelas, which recently died in the Gardens. ,„ _ n „ T . „ 3 " O n two widely contrasted Forms of the Human Cranium, Journal of Anatomy, 1867. PROC. ZOOL. Soc-1880, No. XVI. 16 |