SIWALIK AND NARBADA CARNIVORA. 
65—242 
inner tubercle of pm. 4 is extremely large and bilobate, and placed more posteriorly 
than in .Canis. This disposition is analogous to that prevailing in the generalized 
genus Cynodictis ; and in conjunction with the presence of additional cheek-teeth, 1 
the microdont dentition, and the small size of the carnassial, probably indicates that 
Otocyon is a survival of a primitive form of dog. On the opposite side of Canis to 
Otocyon is Icticyon 2 (considered by Prof. Huxley as subgenerically distinct from Canis), 
in which the number of the cheek-teeth is pm. f, m. { ~1 ; 2 being either absent or 
very much reduced in size, and the inner cingulum of m. 1 wanting : the carnassial 
( pm. 4 ) is relatively large, with a proportionately small internal tubercle, and a 
distinct anterior talon (‘ accessory cusp ’ of Prof. Huxley), of which there is generally 
no trace in the true dogs. 3 This talon is homologous to the anterior talon of pm. 4 
of Hycenarctos (pi. XXX. fig. 2 : a), and its presence in Icticyon (the most specialized 
living dog) and its general absence in Canis, is precisely analogous to its presence in 
Hycenarctos, and its absence in JJrsus. 
The lower carnassial presents an analogous series of modifications : — thus in 
Otocyon 4 the inner cusp of the blade is placed on the inner side of the hinder lobe of 
the same, which it nearly equals in size ; and the line connecting the summits of the 
two (cusp-line) runs nearly at right angles to the long axis of the crown. In Canis 
{woodcut fig. 8) and Cyon the inner cusp becomes in the microdont forms (B J ) 
reduced in size and placed behind the second lobe of the blade, causing the cusp-line 
{a, b) to become oblique ; while in the macrodont forms ( A ! ) these modifications 
become still more developed. In Icticyon , 5 in which m. 3 is absent and m. 2 much 
reduced in size, the inner cusp of the blade has totally disappeared ; and the hinder 
talon of the crown is much reduced and has lost its inner cusp, in consequence of 
which it becomes simply trenchant in place of cup-shaped. 6 As has been previously 
noticed, the alteration in the size and position of the inner cusp of the blade from 
Otocyon to Canis is precisely similar to that which occurs from JJrsus to Hycenarctos. 
The South African genus lycaon {Hycenoides), represented only by L. pictus, has the 
dentition of megalocreodont forms of Canis, but is distinguished by the absence of 
the pollex ; though there is a rudiment of its metacarpal. 
The foregoing observations show that among the existing dogs the specialization 
of the dentition is marked by the gradual reduction in the number and size of the 
hinder cheek-teeth, and in the increasing size, and advancing sectorial character of 
1 The author cannot agree with Prof. Huxley in regarding the occasional presence of m. 4 . and the presence of 5174 in 
Otocyon , as indicative that the immediate ancestors of the group had m. J ; as if such were the case, it is almost certain that 
some of the older canoids would show all these teeth. It is more probable that the presence of these teeth is a mere redundancy, 
perhaps caused, as Ml Filhol supposes, by the length of the jaws. It is, however, unnecessary to apply this explanation, as 
is done by that writer, to the presence of m. 3. 
2 Huxley, op. cit., fig. 16. 
3 As noticed by Prof. Huxley this talon occurs in Canis bengalensis and some other species. 
4 Huxley, op. cit., fig. 13. 5 Ibid, fig. 16. 
6 The writer is unable to accept the classification of the Canidcc proposed by Prof. Cope (‘ Bui. U. S. Geol. Surv.,’ 
vol. VI., p. 178), since the definition of Icticyon is “ heel of inferior molar [carnassial] basin-shaped.” 
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