SIWALIK AND NARBADA CARNIVORA. 
11—188 
basal ridge which sweeps round it.” 1 The foregoing description is taken from some 
typical form like Lutra vulgaris , 2 but there are some slight modifications among the 
existing true otters, although according to Dr. J. Anderson 3 the teeth of all the 
above-mentioned so-called genera into which Dr. Gray subdivided the old genus 
Lutra 4 do not offer a single character of generic value. There are, it is true, in 
some forms external characters like the lateral expansion of the tail in Lutra 
fPteronuraJ sandbachi, and the smallness of the claws in Lutra fAonyxJ leptonyx , 
which may be of generic value. As, however, these are inapplicable in the case of 
fossils, in which the teeth and skull alone have generally to be relied upon, it follows 
that at least for palaeontological purposes all the living forms must be included under 
one genus. In the Indian short-clawed otter Lutra leptonyx (woodcut, fig. 2) and 
other species belonging to the same sub-genus, the palate is relatively short and the 
molars relatively large, and the inner half of m. 1 is the longest part of that tooth, 
while in most other forms the outer half of that tooth is longer than the inner. In 
L. canadensis , however, the proportions of that tooth are the same as in Lj. leptonyx . 
In species like Lutra vulgaris in which the true molar is considerably broader than 
long, the tubercular part of the carnassial is comparatively small, leaving a large 
vacuity between it and the true molar ; but in forms like Lutra (Aonyx) leptonyx the 
squareness of the true molar, and the larger size of the tubercular portion of the 
carnassial leave very little space between these two teeth. These characters are well 
displayed in the figure in the ■■ Histoire Naturelle des Mammiferes,” 5 and may also 
be observed by comparing the woodcut figure 2 with figure 1 of plate XXVII. of 
this memoir. There is, however, among the living species an almost complete 
transition between the. extreme forms of variation in the proportionate size of the 
molar teeth. 
It will be shown below that there is a more important variation in some of the 
fossil forms, but these will be best noticed in the description of the species themselves. 
Turning to the lower dentition it will be found that in typical forms “ the 
tubercular is of comparatively small size, nearly square, and its coronal divided by a 
transverse low ridge into two flattened nearly equal surfaces. The carnassier may 
be considered as made up of two parts, separated by a deep transverse hollow, the 
anterior of which is formed of three sub-equal pointed cusps disposed in a triangle, 
the inner representing the tubercle of the corresponding upper tooth ; the posterior 
portion consists of a dilated flattened tubercle, sloping inwards, and bounded by a 
sharp edge, which is raised at the outer side into an obsolete posterior cusp, less 
distinctly marked at the inner side.” 6 
In all living forms the outer pair of incisors of both jaws is slightly larger than 
the two inner pairs. 
1 Falconer, “ Palaeontological Memoirs,” vol I., p. 332. 2 Blainville, “ Osteographie ” Genus Mustela, pi. VIII. 
3 “Anatomical and Zoological Researches, etc., in Western Yunan,” London, 1878, p. 200. 
4 “ Cat. of Carnivora, etc., in the British Museum,” p. 100, et. seq. 5 V. Gervais, Paris, 1845, p. 116, — woodcuts. 
6 Falconer, loc. cit. 
