201—24 INDIAN TERTIARY AND POST-TERTIARY VERTEBRATA. 
genus ; wliile if L. campani be referred to Enhyclriodon , there is equally no sufficient 
distinction between that genus and Lutra. If L. campani were referred to a new 
genus, and the genus Enhyclriodon retained, the characters of these genera would be 
equally ill-defined, and unsatisfactory, and it seems, therefore, on the whole to be 
the j)referable course to merge all the forms in the genus Lutra ; Enhydrioclon, if it 
be retained at all, not ranking higher than an ill-defined sub-genus, probably including 
L. campani. The variation in the form of the teeth of the genus Lutra as thus 
extended will not be greater than those existing in the genus Ursus. 
Although the foregoing conclusions indicate a considerable range of variation in 
the form, number, and proportions of the dentition of the otters, they do not afford 
any indications of the genetic affinity of the group to the other carnivores. The 
suppression and early shedding of certain of the teeth in Lutra siyalensis indicates 
indeed that this form is even more highly specialized than most of the living otters, 
and that its nearest living ally is L. leptonyx : it cannot, therefore be in any sense 
regarded as an ancestral form of otter ; an inference confirmed by the fact that it existed 
side by side with otters of the same type as the existing species. The most probable 
truly ancestral form of otter is, as already observed, the so-called lutrictis valetoni, 1 
of the miocene of the Continent, in which m. 2 was developed as a minute tooth, while 
m. 1 had not assumed the quadrangular form characteristic of the true otters : and in 
which the four premolars were placed behind the canine, indicating that the shortening 
of the muzzle so characteristic of the true otters had not then taken place. Even in 
Lutrictis , however, the upper carnassial had assumed the characteristic lutrine form, 
indicating that the ancestors of the group, connecting it with the purely land 
mustelines, must be sought in an earlier stage of the world’s history. 
Judging from the 'size of its teeth Lutra sivalensis must have attained to a con- 
siderably larger size than Lutra sandbachi (Gray) 2 of Demerara, the largest existing 
species of otter, the total length of which is given by Dr. Gray as 67 inches (head 
and body 43 in., tail 24 in.) 
Alleged mandible. — On page 337 of the first volume of the u Palaeontological 
Memoirs,” there is published a manuscript note of Dr. Falconer’s relating to the lower 
jaw of a carnivore from the Siwaliks, considered to belong to Enhyclriodon. The 
specimen on which this note is founded is now in the British Museum, and has been 
referred by Mr. Bose to the genus Ganis. 3 
Distribution. — The four skulls mentioned above are the only known remains of 
this species, and it is remarkable that all these specimens were obtained in the region 
of the typical Siwalik Hills, in the neighbourhood of the Ganges and Jumna valleys ; 
and that not a single specimen belonging to this species has been obtained by Mr. 
Theobald, among the thousands of fossils collected by him from the Siwaliks of the 
Punjab. 
1 Gaudry, “ Les Enchainements du Monde Animal, etc., Mammiferes Tertiaires,” fig. 290. 
2 “ Catalogue of Carnivora, etc., in British Museum,” figs. 16-17, pp. 116-7. 
3 “ Quar. Jour. Geol. Soc.,” Vol. XXXVI., p. 135 : vide infra. 
