OCR Text |
Show 272 PROF. HUXLEY ON THE CRANIAL AND [Apr. 6, The upper incisors have the ordinary canine characters ; and the large outer incisor is close to the second. The canines are very strong; and the first three premolars are thick. Although the fourth premolar has a length of only 11 *5 millims., it is 7 millims. thick in front. The inner cusp, however, is very small. In both specimens a small but distinct cusp is developed from the anterior margin of the anterior blade-like cusp of this tooth. This is an unusual feature in the upper sectorial tooth of canine animals; and I am the more careful to draw attention to its existence, as, while Lund had mentioned the fact, Burmeister expressly denies i t : - " Der Fleisch-zahn des Oberkiefers ist ganz Hundeartig, d. h. der innere Neben-hocker sehr klein; und die iiussere Hockerreihe ohne den dritten vordern Hocker, welcher den Viverrinen zusteht" (/. c. p. 9). It is to be presumed therefore that this minute cusp was absent in Burmeister's specimen1. The crown of the first upper molar is triangular and comparatively narrow, in consequence of the reduction of the cingulum and the disappearance of the posterior inner cusp. The crown of the minute second molar is nearly circular, with a median depression separating rudimentary outer and inner cusps (fig. 16, A ) . The lower sectorial presents peculiarities already noted by previous observers. Thus, the inner anterior cusp has altogether disappeared, the heel is very short, and the inner posterior cusp has also vanished. The second lovyer molar is very like the upper, its crown presenting a median depression hounded outside and inside by minute cusps, of which the inner is the lower (fig. 16,B, p. 26'9). Thus the dentition of Icticyon is far more different from that of the ordinary Canidae than that of any other known canine animal, whether recent or extinct, except Otocyon, standing in some respects at the opposite pole to the latter. In all other points, Icticyon is not only, as Lund proved, unmistakably a member of the canine group, but it is so closely allied to the other North-American Thooids, that I can only regard it as a modification of the Canis cancrivorus type, analogous to that which, among the Old-World Jackals, has given rise to Cyon, but carried a step further. In North America the Thooid division is represented only by such macrodont forms as C. latrans and G. lupus (occidentalis). The foregoing Table (XV.) gives the measurements of seven crania of Canis latrans in the British Museum and in the Museum of the Royal College of Surgeons. The exact locality of N o . i. is unknown; No. II. is from Hudson's Bay; N o . in. from Grand Isle, Platte Bock; No. iv. from Medicine Creek, Nebraska; No. v. from Fort Colville; No. vi. from Fort Kearney; and No. v n . from Columbia Biver. They therefore cover almost the whole extent of North America in longitude, and, as might he expected, exhibit a 1 Similar but better-developed anterior basal cusps occur in the upper sectorial of Otocyon, and occasionally in other Canidaj, as C. anthus, C. zerda, and C. bcti-gacensis. Hence no great taxonomic importance can be assigned to this character. |