CRANIAL CHARACTERS OF THE SNAKE-RAT. 67 
Brown Rat (Mus decwmanus), which is quite different. If there- 
fore the new rat is a mere variety of either of the two species 
which have been long known as members of the British mamma- 
lian fauna, and which have always been considered specifically 
distinct, it must be deemed a variety of Mus rattus; but I claim 
for it distinctive characters separating it from that rat, quite as 
marked as those which distinguish the Brown from the old English 
Black Rat. Indeed Mus decwmanus more nearly resembles Mus 
rattus than does the new rat. It was suggested to me, at the 
time I exhibited the living specimens, that an appeal must be 
made to the cranial characters of each, before the distinctness and 
the degree of distinctness between the two could be established. 
The result of this investigation I now give to the Society. 
On the table are the skulls of the identical rats that were for- 
merly exhibited—two adult males ; and I have also some enlarged 
outline drawings (from which the accompanying woodcuts were 
taken) showing the salient peculiarities of each cranium. The 
Fig. 1. Fig. 2. 

Top view of Cranium of Snake-Rat. Top view of Cranium of Mus rattus. 
Enlarged two diameters. Enlarged two diameters. 
5* 
