OCR Text |
Show 382 DR. ST. G. MIVART ON THE ARCTOIDEA. [Apr. 21, The cranial characters have been, in the main, given by Prof. Flowerl. Besides these it may be noted that the outline of the skull seen in profile has a rather striking resemblance to that of some of the larger Cats. The muzzle is very broad, more so relatively than in any Arctoid yet noted except Conepatus and Ailurus. It is prolonged backwards behind the last molars, though hardly more so than in Mellivora, and it has not so definite a lateral boundary as in the latter, though the pterygoids show a tendency to descend below the general level of the palate 2. The maxilla forms but a small floor to the orbit. The zygomata extend much outwards, owing to the breadth of the glenoid surfaces. The sagittal ridge is much as in Mellivora, The glenoid foramen is very large. A slight ridge connects the paroccipital and mastoid processes, and the latter, though conspicuous, does not depend below the meatus auditorius externus. The stylo-mastoid foramen is very conspicuous. The infra-orbital foramen is moderate or rather small. The angle of the mandible is little conspicuous and is pressed upwards, though not so much so as in Arctonyx and Mydaus. Molar formula=P. \, M . |. The dentition considerably resembles that of Mellivora, as to the form of teeth, not of course as to their number. The outermost upper incisor, however, is very large and caninelike. The fourth upper premolar is relatively larger than in Mellivora-especially its hindmost cusp ; the first upper molar is a little more equal in length externally aud internally than is generally the case in the last-mentioned genus. The fourth lower premolar has only one hinder cusp and that smaller-thus resembling Galictis. The first lower true molar is larger than in Mellivora. There is a very small heel and no inner tubercle. There is a second true molar, which is a small, rounded tooth. The dentition is very sectorial, at once more sectorial and powerful than in any other Arctoid. It may therefore be interesting to compare its dentition with that of one or two other specially predacious carnivora. Gulo compared with Felis-has the incisors relatively larger. The third upper premolar is rather smaller with the main cusp less relatively produced, the fourth upper premolar, or upper sectorial, has its fore-cusp smaller, its hind cusp large and more equal in development to the mid-cusp, and the internal cusp larger. The first true molar is also much larger. In the lower jaw the third premolar is less trilobed than in Felis and its principal lobe is less developed. The sectorial, or first true molar, differs by having a large heel, and in having the two principal cusps less lofty. There is a second true molar. Gulo compared with Hyaena and Felis.-The incisors are not so large relatively as in Hyana, and the other ones are less preponderating. In these respects Gulo is more like Hyana than Felis. The third upper premolar is much smaller relatively. The hind cusp is less marked and little produced. The fourth premolar has 1 P. Z. S. 1869, p. 12. 2 See above, p. 373. |