1900.] MLTS SYLVATICUS AND ITS ALLIES. 403 



specimen collected at Oporto, Portugal, by Mr. James Searle, on 

 December 12th, 1896; but too much must not be inferred from a 

 single specimen, which may possibly indicate the existence of 

 Mas s. celticus in the west of Portugal, or may be only an acci- 

 dental variety. Blasius, however, kuew of the occurrence of dark 

 Field-mice in the higher mountains of Europe K This single 

 specimen from Oporto, whatever it may be, is certainly very unlike 

 the ordinary Portuguese Eield-mice. 



A remarkable fact is the occurrence of this mouse on the same 

 island (Lewis) as the very distinct M. s. hebridensis, which is one 

 of the larger forms of -Field-mice. I am informed by Mr. de 

 Winton that the latter keeps to its own part of the island, and 

 that probably the two do not intermingle. It is curious that while 

 a big and little form of Mus sylvaticus occur here side by side, 

 each finds a different method of fitting itself for the damp dull 

 climate of the west. 



It is interesting to find that the Field-mice of the centre and 

 east of Ireland are normal, and, as far as I can make out, show 

 neither any darkening of the colour of the upper surface nor any 

 diminution of size. Among these normal Irish mice must be 

 included specimens from Ballaghmoon, Co. Carlow (Mr. J. G. 

 Symes), from Cashel, Co. Tipperary, and from the neighbourhood 

 of Arthurstown, Co. Wexford, together with those in the Dublin 

 Museum from Cos. Dublin, Wicklow, and Louth. 



3. MUS SYLVATICUS HEBHIDENSIS. 



Mus hebridensis, W. E. de Winton, Zoologist, Oct. 1895, p. 369. 

 Mus sylvaticus hebridensis, W. E. de Winton, Zoologist, Nov. 

 1895, p. 426. 



Type. No. 95.10.25.1 (British Museum Collection), from Barra, 

 Outer Hebrides (W. E. de Winton). 



Distinguishing Characteristics. Resembles Mus sylvaticus inter- 

 medius in general form and colour, but is larger (about equal to 

 M. s. wintoni), and has proportionately smaller ears, larger hind feet 

 (especially stout in males), shorter and thicker tail, and generally 

 stouter build. The colour of the upperside is more uniform and 

 less bright than in M. s. intermedius ; that of the underside is 

 " generally dusky or sandy, with no distinct line between the 

 upper and under parts" (de Winton); that of the tail is almost 

 uniformly " brownish grey." 



Skull large : total length of that of the type specimen 27 mm. 



Distribution. The islands of Lewis and Barra in the Outer 

 Hebrides. 



General Remarks. This island-form was first obtained by Mr. J. 

 Steele Elliott ; but to Mr. de Winton is due the credit of having 

 written the first published notice 2 of so interesting an addition to 

 the British fauna. 



1 Saugethiere Deutsch. p. 324 (1857). 



2 Ann. Scott. Nat, Hist., Jan. 1895, p. 53. 



