ENHYDRIODON. 



335 



very different family, the Euminantia, where the upper 

 lateral incisor puts on the form and development of a canine, 

 in the Camel. In one of the specimens (fig. 2), the base of 

 this tooth, with the other incisors, remains in the jaw, broken 

 off on a level with the alveolus, and enables us to determine 

 its relative size with precision. The section of the fang 

 shows a very broad oval ; the dimensions, as contrasted with 

 those of a large Indian Otter, are ' : — 



Antero-posterior diameter outer incisor 

 Transverse ditto ditto 



Antero-posterior diam. middle incisor 

 Transverse ditto .... 

 Antero-posterior diam. of inner incisor 

 Transverse of ditto .... 



Enhydrio- 

 don 



Inch 

 •45 

 •37 

 •33 

 •14 

 •25 

 •09 



Indian 

 Otter 



Inch 



•17 



•12 



•14 



•1 



•09 



•08 



In the younger animal, to which the head (fig. 2) belonged, 

 the incisors are all present; but in the older head (fig. 5), 

 the middle incisors are not only wanting, but the alveoli are 

 completely filled up and obliterated, there being nothing but 

 a blank space between the outer incisors. In this deciduous 

 character of the middle incisors Enhydriodon agrees with the 

 modern Ursus (Prochilus) labiatus, or so called Sloth Bear of 

 India, in which the incisors drop out as the animal increases 

 in age. None of our specimens show what the number and 

 character of the incisors were in the lower jaw ; but such a 

 strongly-developed lamarian tooth in the upper must in all 

 probability have had something corresponding to oppose it 

 in the lower jaw; we therefore infer that there were two 

 large outer incisors, one on each side, below, and that the 

 four middle incisors were also present, for in Enhydra, where 

 there is a suppression of two incisors, it is the outer one on 

 each side that disappears, the central ones remaining. This 

 is proved by the form of the exhibited incisors.^ 



The canines of the upper jaw, like the lateral incisors, 

 were proportionately large, and of great strength and mas- 

 siveness. A section of the right one is got in the head 

 fig. 5, of a circular form. The dimensions are, antero-posterior 



diam. 5^ lines, transverse do 



' The measurements, which were 

 omitted from the original MSS. have 

 been filled in by me from specimens in 

 the British Museum. — [Ed.] 



" j-Ir. Martin, in the abstract of his 

 paper on Enhydra, contained in the 

 Proceedings of the Zoologl. Society for 



4|. In the head, fig. 2, both 



June 14, 1836, appears to consider that 

 the suppressed incisors in the lower jaw 

 of Enhydra belong to the middle ones. 

 But a close examination of the form of 

 the teeth leads to the conclusion stated 

 above. 



