KtJNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 40. N:0 5. 23 



rats caught belonged to the native råts or the ones latest introduced, because at the 

 time when the rats actually were caught among the tussock, an invasion of rats 

 from the ship had taken place and it is uncertain how far they could have spread 

 themselves although it is most probable that they kept themselves round the fac- 

 tory where food was to be gotten in abundance. 



One of the three rats caught among the tussock, viz. the one killed by the 

 dog differs considerably from the common Mus norvegicus with regard to the colour 

 of the fur. It is decidedly more reddish or rusty brown in the general colour than 

 the common rat. The longest hairs, which dominate on the back, are tipped with 

 blackish brown. The other hairs are rusty red or rusty yellow. These glisten through 

 the blackish hairs on the back and dominate on the neck and crown. The nose 

 and the sides of the head are covered by brown and buffish hairs mixed, the for- 

 mer dominating. The chin and the throat are white, the lower side of the neck 

 whitish with a stitch in yellow, the breast and the belly påle sulphur yellow. On 

 the sides of the body the colours of the back dominate but hairs coloured as those 

 of the belly are mixed in and produce a brindled appearanee. The feet are whitish 

 grey and the tail is greyish brown. The lower and longer whiskers are white the 

 upper and smaller blackish. 



The other two specimens are similar to this one but the yellow shade of the 

 belly is less pronounced. These two specimens are not quite fullgrown, which may 

 explain the difference. 



The skull is similar to that of the typical Mus norvegicus but in one of the 

 specimens the interparietal is circumscribed in front and behind by equally curved 

 lines and ends laterally in sharp points, in another it is rhomboidic in shape and 

 blunt at the lateral ends. The series of cheek-teeth is shorter than the length of 

 foramina incisiva. 



For comparison Sörling caught some rats on board the ship and they looked 

 like common rats. When skinning the different specimens it was found that the rats 

 caught in the tussock have a much thicker skin than those caught on board the 

 ship. The former have also a denser and longer fur which of course is an adapt- 

 ation to the climate. It thus appears as if the South Georgia rat had undergone 

 some change since its introduction, even if it is not very great. Its maximum age 

 on the island cannot be more than about 100 years and.it is probably less. 



