V. 



A Fish-Eating Kodent. 



AVERY interesting new Mammal has recently been received at the 

 British Museum, in the form of a Fish-eating Rat from the 

 mountain streams of Central Peru. The animal is of about the size 

 of a common house-rat, but has a flattened head, strong and 

 numerous whisker-bristles, and very small eyes and ears, characters 

 which give it a striking resemblance in its physiognomy to some of 

 the aquatic genera of the Insectivora and Carnivora, such as Potaino- 

 gale, Myogale, Lutra, or Cynogale. Its swimming powers are evidently 

 very great, as is shown, among other things, by its broad, webbed and 

 strongly-ciliated hind feet, far better developed for this purpose than 

 are those of the ordinary swimming Muridae, such as our English 

 Water-vole, whose simple vegetarian diet does not necessitate the 

 development of any exceptional swimming powers. In colour, like 

 the common Water Shrew, it has a dark upper side with a whitish 

 belly, and has a markedly bicolor black and white tail. 



The chief interest of the new form centres in the fact of its 

 being wholly a fish-eater, and in its having in connection therewith its 

 incisor teeth modified for catching a slippery, active prey by the 

 development of their outer corners into long sharp points, , and its 

 intestines altered by the reduction almost to nil of its ccecum, an organ 

 in vegetarian Muridae always of great size and capacity. The stomach 

 of the single specimen obtained contains fish-scales, recognised by Mr. 

 Boulenger as those of Tetragonopterus alosa, a fish whose average length 

 is about six inches. 



This animal represents quite a new departure in Rodent life- 

 history, for although it is now perfectly well known that the North 

 American Musquash [Fiber zibethicus) occasionally feeds on fish 

 caught by itself, yet there is no other Rodent which, as in the case of 

 Ichthyomys stolzmanni, as it is proposed to term the new form, wholly 

 lives on fish, to the exclusion of a vegetable diet. 



The general relationships of Ichthyomys are clearly with the ordi- 

 nary South American Muridae, perhaps more especially with those 

 of the Habrothrix group, and there is certainly no direct connection 

 with Fiber. 



The type and only known specimen of this interesting form was 

 obtained by the Polish collector, Mr. J. Kalinowski, at Chanchamayo, 

 Central Peru, in the course of i8gi. 



Oldfield Thomas. 



