ENHYDRIODON. 333 



by a deep transverse hollow, the anterior of which is formed 

 of three sub-equal pointed cusps disposed in a triangle, the 

 inner one 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. 



The false molars, canines, and incisors of the Otter agree 

 so closely with those of other Mustelidce as not to require 

 special notice. In regard to the ' wear ' of the molars gene- 

 rally, we may remark that from age and use they get blunted 

 and irregularly ground down ; but the cusps never wear off 

 into the truncated depressed transverse discs exhibited in 

 the teeth of Hyaenas, a remarkable approach to which takes 

 place in those of Enhydriodon, to be noticed more particularly 

 in the sequel. 



In the Enliydra the teeth undergo a singular modification, 

 both m number and conf]gu.ration. It has normally the 

 same amount of molars in the lower jaw as the true Otters, 

 and one false molar less in the upper jaw, so that the 

 dental formida, if regularly followed out in the canuaes and 



incisors would be rg = 34; but from a peculiar suppression 



there are only four incisors in the lower jaw, the outer and 

 largest one on each side being wantmg. The canines are 

 only remarkable for their small size in relation to the other 

 teeth and the bulk of the head. 



But it is in the form of the molars of Enliydra that the 

 great deviation from the tj^e of the Otters is observed. They 

 are large, robust, and amorphous : the coronal being com- 

 posed of a very thick layer of enamel. Everything like the 

 pointed cusps and trenchant edges of the Otters' teeth has 

 disappeared, and given place to a flattened, sinuous, and 

 obtusely tuberculated surface, like the worn tubercular teeth 

 of the Bears. This is not a result of age, but is shown in 

 the young animal when the sutures of the head are still 

 open. Notwithstanding this disguise, the amorphous-like 

 inequalities can be traced to a modified representation of the 

 cusps and lobes of the teeth in the Otter. The vipper 

 carnassier is of a triangular form, divided by a longitudinal 

 furrow, the outer portion being formed of two very obtuse 

 rounded tubercles, the anterior of which is the largest, 

 representing the central cusp of the carnassier of the Otter ; 

 but there is no trace of the anterior lobe of the latter. The 

 internal portion is still larger than in the Otter, and consists 

 of an expanded disc raised into a third obtuse tubercle, and 

 bounded by a blunt basal ridge. The upper tubercular is of 



