The Mustelidee present great constancy in regard to the number of their true molar teeth ; with one exception, the Ratel vora), in which M. 2 is absent below, they have one true molar on each side of the upper jaw, and two on each side of the lower jaw; the second of these has always a broad tubercular crown, like the one above. The upper true molar is supported by one inner, and sometimes by one (Putorius, Gale), sometimes two (Mustela, Lutra, Melphids), outer fangs. The second true molar below is also tubercular, but has a single fang. The crown of the first true molar below offers many gradations from the sectorial type, as manifested in Putorius and Gule, to the tuber cular type, as in the Taira, Ratel, and sea otter. The principal varieties occur, as usual, in the comparatively less important premolars : in the Martins and Gluttons, they are as numerous as in the dog ; the first, in both jaws, being implanted by a single fang ; the rest by two, with the exception of the last above, which lies three roots. In the otter, we find the first premolar removed from the lower jaw ; and the second (now the first) shows its true homology by its double implantation, as well as by the position of its crown behind the first in the upper jaw (p. 1). In the Stoats, Skunks, and Ratels, the premolar series is further reduced by the loss of the anterior tooth (p. 1) in both jaws, and by the diminution of the size of p. 2, which thus becomes the first in both jaws, and which is also now implanted by a single fang. In a South American Skunk, the second premolar disappears in the upper jaw, leaving there only the homologues of the third and fourth of the typical formula, p, 4 being always the sectorial in the Afustelidee, as in other terrestrial Carnivora. This tooth, under all its modifications, retains the blade with the lobe, corresponding to the middle one in the feline sectorial, generally well developed and sharp-pointed ; the differences are principally manifested by the proportions of the inner tubercle, and the relative size of the third root supporting it. But the upper sectorial, being a premolar, and therefore requiring less modification of the crown to adapt it for its special functions„ manifests a more limited extent of variety than the lower sectorial, which, being a true molar, requires greater modification of the typical, form of its crown to fit it for playing upon the sectorial blade of p. 4 above, Melidco. —In this subfamily I comprise the European Badger (Meles), the Indian Badger (Arctony.r), and the American Badger (Ta.videa) ; which, with respect to their den.. tition, stand at the opposite extrcine of the Mustelida to that occupied by the predaceous Weasel, and manifest the most tuberculate and omnivorous character of the teeth. The formula is :—i 1-1 3-3 m. . • c. — • ) — • 3—s3 ; ' • 1--1 30, The canines are strongly developed, well pointed, with a posterior trenchant edge ; they are more compressed in Arctonye than in Metes. The first lower premolar (p. 1) is very small, single-fanged, and, soon lost. The first above, corresponding with the second in the dog, is also small, and implanted by two connate fangs. The second upper premolar (p, 3) has a larger, but simple, sub-compressed conical crown, and is implanted by two fangs : the third (p. 4) re peats the form of the second on a larger scale, with a better developed posterior talon, and with the addition of a tri-tuberculate low flat lobe, which is supported by a third fang : the outer pointed and more produced part of this tooth represents the blade of the sectorial tooth and the entire crown of the antecedent premolars. The true molar in Meles (nn. 1) is of enormous size compared with that of any of the preceding Carnivora: it has three external tubercles, and an extensive horizontal surface traversed longitudinally by a low ridge, and bounded by an internal belt, the cingulum of Illiger: this tooth has a similarly shaped, but relatively smaller, crown in Arc tonyx.* The second premolar below (p. 2) is commonly the first, through the early loss of the minute one in front ; its fangs are usually connate, as in its homotype above. The third and fourth premolars slightly in crease in size, have simple compressed conical crowns, and two fangs each. The first true molar below (m. 1) now retains little of its sectorial character, the blade being represented only by the two anterior small, compressed pointed lobes; behind these, the crown ex pands into an oval grinding surface, narrower in Arelonyx than in Meles, supporting three tubercles and a posterior tuberculate ridge : it has generally two principal roots and a small intermediate accessory fang, as in the otter. The second molar (m. 2), which ter minates the series below, is of small size, and has a rounded flat crown, depressed in the centre, and with two small external tubercles; its two short fangs are connate. In the
Labrador Badger, the last premolar has a larger relative size, the part corresponding with the blade of the sectorial, is sharper and more produced, and the internal tu bercle has two lobes; the succeeding molar tooth is reduced in size, and its crown pre sents a triangular form. The first true molar below has its sectorial lobes better developed : these differences give the North American badgers a more carnivorous character than is manifested by the Indian or European species.
Sub-Ursidce.—In other allied genera, which, like the badgers, have been grouped, on ac count of the plantigrade structure of their feet, with the bears, a progressive approxi mation is made to the type of the dentition of the Ursine species. The first true molar below soon loses all its sectorial modification, and acquires its true tubercular character : and the last premolar above becomes more directly and completely opposed to its homo type in the lower jaw. The Racoon ( Procyon t) and the Coati (Hague) present good examples of these transitional modifications ; they have the complete number of premolar teeth, the . 33 — dental formula being, i. — P ' 3-3' 1-1' - 4-4 4-4' vz. 40. The development of the in ner part of the crown of the last upper pre molar, which constitutes the tubercle of the sectorial tooth, now produces two tubercles on a level with the outer ones which represent the blade; and the opposite premolar below (p.4), which is the true homotype of the modified sectorial above, begins to acquire a marked increase of breadth and accessory basal tu bercles. All the lower premolars, as well as the true molars, have two fangs; the three first premolars above have two fangs, the fourth has three, like the two true molars above.
The dental formula of the Indian Bentu rong (Arctictis) and Kinkajou (Cercoleptes) is . 3-3 I—I 3-3 2-2 — — • = 36.
3-3' 2-2 : Phocidce.— We have seen a tendency to deviate from the feriae number of the incisors in the most aquatic and piscivorous of the Musteline quadrupeds, viz. the sea-otter (Enhydra), in which species the two middle incisors of the lower jaw are not developed in the permanent dentition. In the family of true seals, the incisive formula is further re duced, in some species even to zero in the lower jaw, and it never exceeds the Phocidce possess powerful canines ; only in the aberrant walrus ( 7'richechus) are they absent in the lower jaw, but this is compensated by the singular excess of development which they manifest in the upper jaw. In the pinnigrade, as in the plantigrade, family of Carnivores we find the teeth which correspond to true mo lars more numerous than in the digitigrade species, and even occasionally rising to the typical number, three on each side ; but this, in the seals, is manifested in the upper and not, as in the bears, in the lower jaw. The entire molar series usually includes five, rarely six teeth on each side of the upper jaw, and five on each side of the lower jaw, with crowns, which vary little in size or form in the same individual ; they are supported in some genera, as the Eared Seals (Olariw) and Elephant Seals (eystophora#), by a single fang ; in other genera t by two fangs, which are usually connate in the first or second teeth ; the fang or fangs of both incisors, canines and molars, are always remarkable for their thickness, which commonly sur passes the longest diameter of the crown. The crowns are most commonly compressed, conical, more or less pointed, with the " cin gulum " and the anterior and posterior basal tubercles more or less developed; in a few of the largest species they are simple and ob tuse, and particularly so in the walrus, in which the molar teeth are reduced to a smaller number than in the true seals.$ In these the line of demarcation between the true and false molars is very indefinitely in dicated by characters of form or position ; but, according to the instances in which a deciduous dentition has been observed, the first three permanent molars in both jaws succeed and displace the same number of milk molars, and are consequently premolars ; occasionally, in the seals with two-rooted molars, the snore simple character of the premolar teeth is manifested by their fangs being connate, and in the Stenorhynchus serri dens the more complex character of the true molars is manifested in the crown. There is no special modification of the crown of any tooth by which it can merit the name of a " sectorial " or " carnassial • " but we may point with certainty to the third molar above and the fourth below as to those teeth which manifest the sectorial character in the terrestrial Carnivora.