MUSTELID^. 



497 



rated by any interspace : the first and second premolars have ob- 

 lique obtuse conical crowns. The third premolar is more than twice 

 the size of the second and supports a large anterior hemispheric 

 protuberance with a small internal tubercle and a posterior basal 

 ridge. The first true molar has an oblong quadrate crown with 

 an anterior small tubercle, a larger and more prominent inner one, 

 and the rest of the broad horizontal surface undulating. The 

 second true molar has a transversely elliptical crown depressed in 

 the centre. When the teeth are in apposition, the anterior third 

 of the first true molar below is applied to the inner tubercle of 

 the last premolar above ; the rest of its crown plays upon that of its 

 analogue the first true molar in the upper jaw, leaving a small 

 part of that tooth to receive the appulse of the second true molar 

 below, which has no corresponding tooth in the upper jaw. 



The MustelidcB present great constancy in regard to the 

 number of their true or post-molar teeth; with one exception, 

 {Mellivora), the lower molar series of which is figured at PI. 128, 

 fig. 10, showing the absence of the second true molar, 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, Gulo), 

 sometimes two {MustelUy Lutra, Mephitis), 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 Gulo, to the 

 tubercular type as in the Taira, Ratel (PI. 128, fig. 10 m I) and 

 Sea-Otter (ib. fig. 12 m 1) ; it is usually supported by two fangs ; 

 a small intermediate supplemental root is occasionally developed, as 

 in the example from the Otter figured by M. de Blainville, {Osteog. 

 de Mustela, PI. xiii.) The principal varieties occur, as usual, in 

 the comparatively less important premolars : in the Martins and 

 Gluttons (PL 128, fig. 7) 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 has three roots. In 

 the Otter (ib. fig. 4) we find the first premolar removed from the 



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