Mr. Waterhouse on new species oJMus, 4-13 



neric title Mus, I have here to state that the above species natu- 

 rally divide themselves into several subordinate groups, the characters 

 of which are sufficiently evident, not only between themselves, but 

 also between each group and that to which the term Mus ought, I 

 conceive, to be restricted, and of which our common mouse {Mus 

 musculiis) may be regarded as the type. To these groups I shall here 

 assign subgeneric titles, and at the same time point out their chief 

 distinguishing characters without entering into any minute details 

 respecting them, as I sliall shortly have an opportunity of illustrating 

 my views by means of drawings both of the teeth and of the animals, 

 without which it is impossible to convey a clear idea of the subject/* 

 Subgenus 1. Scapteromys*. 

 Molars with enamel deeply indented in the crown. In the front 

 molar of the lower jaw the enamel is indented twice on the outer 

 margin and three times on the inner; in the second molar the enamel 

 is indented once on the outer margin and twice on the inner ; and 

 in the last molar once on the outer, and twice on the inner. Fur 

 long and soft. Tail moderate, well clothed with hair. Claws long, 

 but slightly curved and formed for burrowing. Fore-feet mode- 

 rately large. Thumb furnished with a distinct claw. Ears moderate, 

 well clothed with hairs. 



Species Mus {Scapteromys) tumidus. 



Subgenus 2. Oxymycterus t. 

 Molars with the folds of enamel penetrating deeply into the body 

 of the tooth. Front molar of the lower jaw with three indentations on 

 the inner side and two on the outer ; second molar with two on the 

 outer side and the same number on the inner ; the last molar with 

 one indentation of the enamel on each side. Fur long and soft. 

 Claws long, but slightly curved, and formed for burrowing. A di- 

 stinct claw on the thumb. Tail short, moderately furnished with 

 hair. Nose much elongated and pointed. 

 Species Mils {Oxymycterus) nasutus. 



Subgenus 3. Abrothrix|. 

 Folds of enamel penetrating deeply into the sides of the molars. 

 The front molar of the lower jaw has three folds of enamel on the 

 inner side and two on the outer ; the second molar has two on the 

 inner side and one on the outer ; and the last molar has one on each 

 side. Fur long and soft. Tail short, well furnished with hair. 

 Thumb vdth a short rounded nail. Ears well furnished with hair. 



Type Mus {Abrothrix) longipilis. 



Species 2 Mu^ (-46.) obscurus. 



.„____ 3 olivaceus. 



4 micropits. 



»______ 5 br achy Otis. 



6 xanthorhinus, 



' 7 canescens. 



8 • arenicola, 



• Scapteromys, from 2««TT»jg, a digger, and My;, 

 t Oxymycterus, from O^vj, sharp, and Mj/«t»jj, n< 

 X Abrothrix, from ' A/3go^ soft or delicate, and ©g/ 



m O^vs, sharp, and Mvktvi^, nose. 

 A/3go^ soft or delicate, and ©g/$, hair. 



