CHIMAEEOGALE. 143 



marked by two obscure ridges from before backwards, the surface between them 

 being rather flat. The canine tooth has no character of its own to separate it from 

 the foregoing. All these teeth overlap each other by their anterior extremities. 

 The first molar has the greatest vertical extension of any of the teeth except the 

 front incisors. Externally it has two cusps, the anterior small, and the one behind 

 it much larger and trenchant, with a long ridge running backwards that might 

 almost be regarded as another cusp. At a higher level internally there are two 

 other cusps, the anterior the most vertically extended of the two, but rounded, 

 while the posterior cusp has a longish, posterior ridge. The second molar has three 

 external, two median, and two internal cusps ; the posterior median cusp being the 

 longest. The anterior median cusp is very small, and is connected with the anterior 

 and middle external cusps by a low ridge to each. The posterior internal cusp is 

 about half the size of its fellow in front of it. In the third molar, the middle 

 external cusp is much smaller than the anterior, and the posterior median cusp has 

 but slight vertical extension. The last molar is less than half the size of the tooth 

 before it. Its crown is triangular, with its base inwards and backwards and its apex 

 forwards and outwards. Externally there are very obscure indications of the tricus- 

 pidate nature of that margin, and internally the existence of two very feeble cusps 

 can be detected with difiiculty. 



The lower incisors are not marked by any ridges, they arch forwards and 

 upwards. The canine is the smallest tooth, minute, and like an upper lateral incisor. 

 The premolar is conical, with two cusps viewed from without, the anterior forming 

 the body of the crown with a small prominence on its hinder margin. The first 

 molar has the greatest height. It has three external cusps, of which the middle 

 cusp is the highest, and is closely applied to its fellow of the outside. The 

 anterior, external cusps form the front end of the teeth, and are on a line with the 

 internal cusps on the molars. The second molar only differs from the first in being 

 slightly smaller, and the third from the second in being little more than half its 

 size, with much more feebly developed cusps. 



The dental formula may be stated thus, judging from analogy, viz., — 



2 + 4 , 2 , 8 9Q 



-2- + 2 + 2T6— ^^* 



This aquatic mammal in its white teeth and in their number is closely allied 

 to the terrestrial Crocidurce, but it differs from them, as stated, in having a process on 

 the inside of the front incisors. The existence, however, of such a structure by itself 

 would not have been of sufficient importance to separate it from Crocidura; but when 

 it is taken in connection with the modifications of the skeleton which adapt the 

 Soricine type of structure which it retains, to an aquatic habit, we are entitled to 

 separate it generically: although judging it, by its teeth alone, it would scarcely be 

 entitled to generic rank. 



The skeleton of this animal is of extremely light construction compared with 

 the heavy skeleton of terrestrial shrews attaining similar dimensions, but in its 

 general character it conforms to the shrew type of skeleton. The character which 



