ON THE IDENTITY OF THE IRISH RAT. 5 



We know, however, of one parti-coloured rat,* but whether it 

 was the offspring of a cross between Mus decumanus and Mus 

 hibernicus it is impossible to say. In this specimen, which was 

 trapped at Kilmanock, the predominating colour was brown, with 

 the shoulders and tail black, while a black line extended the whole 

 length of and along the median line of the back. To add to its 

 singular appearance the head was marked with white. 



In two nests of young rats which were found in the winter of 

 1889-90 it is interesting to note that all the young were black. 

 One of these nests contained five young. The haunts frequented 

 by M. hibernicus are precisely similar to those of its brown brother. 

 We have had specimens from dwelling-houses, from the upper 

 storey of a granary, from the banks of a pond, and from rabbits' 

 burrows. 



FIG • 



riG 2 



r\ 



Fig. 1. Skull of Mus rattus and M. alexandrinus. Fig. 2. Skull of Mus 

 decumanus and M. hibernicus. Seen from above and from behind. 

 F = Frontals. P = Parietals. I-P = Interparietals. S = Squamosals. 

 Z = Zygomata. 



No difference has been detected in the habits of the two 

 forms. They are frequently found in the same hole ; and young 

 of both kinds have been seen playing together. Mr. Gibbon, 



;< Described in 'The Zoologist' for 1889, p. 142. 



