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Show 402 MR. G. E. H. BARRETT-HAMILTON ON [APr- 3> like so many other local forms, were put aside with the remark that they could be only regarded as " varieties of 3Ius sylvaticus "l. Irish naturalists, however, well knowing tbe tendency of the elements of our fauna to become darker in the west of the country, have all along suspected that Jenyns's suggestion was well worthy of attention. Hence they have been gradually accumulating a series of Field-mice from Ireland, with the result that I think I may now say definitely that we have, in tbe west of Ireland, a small dark subspecies of Field-mouse, which nearly corresponds to Jenyns's description, aud which is quite unlike the Field-mice of the greater part of Europe, of England, or, what is equally interesting, of the east and centre of Ireland. For this small subspecies I propose the name Mus sylvaticus celticus. The first specimens of this Mouse received at the Museum were a series of six, collected by Col. J. W . Yerbury, at Caragh Lake, Co. Kerry, between Nov. 27th and Dec. 1st, 1894. These, although some allowance must be made for the winter coat, are darker and smaller than any English specimens which I have seen even of that season. In spite of these characters, I at first hesitated to regard the specimens as conclusive evidence of the truth of Jenyns's hypothesis. It was possible that in such a mild climate the mice might continue breeding to a late date in the year, so that examples showing the characteristics of immaturity might be obtainable even in December, and hence Col. Yerbury's specimens might possibly be regarded as not wiiolly adult. The colour of the underside, however, did not suggest immaturity, it being as white and as clearly marked off from that of the upperside as in any English examples, nor were the skulls those of immature specimens. Hence I felt sure that I should eventually obtain others like them from the west of Ireland. These were forthcoming in 1896, when Mr. B. F. Hibbert sent m e four small dark JMice from Woodpark, Co. Galvvay. The date at which they had been taken (February and March) was such as to almost preclude the possibility of their being immature, and they were further supplemented by a third set of the small dark w-estern Mouse sent by Mr. G. A. Passingham, from Fermoyle, Castlegregory, in the very same county which had produced both Jenyns's and Colonel Yerbury's specimens. The interest of these specimens was heightened when I found them exactly matched in colour and size by three collected at Eisken, in Lew is, in the Outer Hebrides, in October and November 1895, and by one sent to the British Museum of Natural History by Mr. J. Steele Elliott, from Skye, in tbe same year. These specimens seem to indicate that this small Western subspecies of 31us sylvaticus is not confined to the west of Ireland, but is found in similar localities in the Western Scotch Isles. The late date of capture (June 24th) of the Skye specimens shows that the dark colour is not characteristic of winter, but is retained throughout the year. It is remarkable that I should have seen a perfectly similar 1 See Bell's ' British Quadrupeds,' ed. ii. p. 296 (1874). |