TRUE POSITION OF MUS BATTUS. 203 



M. rufescens, Gray, Ann. Mag. Nat. Hist. vol. i. p. 585 (1837). 



M. nitidas, Gray, Ann. Mag. Nat. Hist. vol. xv. p. 267. 



Local Names. — Black Rat ; Old English Black Rat ; Alex- 

 andrine Rat (English). Black Ratton ; Blue Rat (Scottish). 

 Rodan-dubh ; Radan-dubh (Scotch Gaelic). Llygoden fferngig 

 (Welsh) . " French " Mouse (Irish) . 



Characters. — The " Black " Rat is not so stoutly built as the 

 Brown Rat, and it has a proportionately longer tail and larger 

 ears. The tail is generally, but not always, longer than the head 

 and body, and the ears are about half the length of the head. 

 Mammae, 10 or 12. 



Three well-marked races of the so-called " Black" Rat exist 

 in our islands, and the fact that all interbreed freely* has led to 

 some confusion amongst naturalists, who perhaps have only had 

 the opportunity of handling a few specimens. I have examined 

 a very large series of the species taken in different localities 

 within the past fifty years, and consider that there are three 

 distinct races, namely, the Alexandrine Rat, the British Alex- 

 andrine Rat (i.e. the misnamed Old English "Black" Rat), and 

 the Black Alexandrine Rat. The first mentioned is undoubtedly 

 the true species, of which the two last named are subspecific 

 races. 



Subspecies 1. — The Alexandrine Rat (Mus rattus alexandrinus). 



The colour on the upper surface of this race is very similar 

 to Mus decumanus (the Brown Rat), yellowish brown, intermixed 

 with black hairs. The black hairs predominate, and are longest 

 over the thighs and rump. The ventral surface, breast, throat, 

 lower lip, and edges of the limbs are yellowish white. The upper 

 part of the fore legs and along the line of demarcation between 

 the two surfaces is pure grey. Compared with Mus rattus ater, 

 the coat seems somewhat sparse. Tail long and furnished with 

 rings of scales, and covered with short black lines. Ears large, 

 naked, and well rounded ; vibrissa long and black. Soles naked 

 and yellowish. 



Measurements of an adult male from Yarmouth : — Head and 



* M. de L'Isle made experiments with interbreeding, and concluded that 

 M . rattus and M. alexandrinus were geographical races of the same species, 

 and that M. alexandrinus was the older and parent form. 



b2 



