On British z~brms of Apodemus. 117 vein 2 to inner margin, a small spot at middle of inner margin and postmedial patch from vein 4 to inner margin with small spot beyond its upper extremity ; a white strcal< striated with red-brown at middle of costa, small postmedia| spot on costa, and oblique rather maculate band from costa before apex to termen at vein 4, with a small spot beyond it below apex. Hind wing grey striated with brown ; a white antemedial patch in and below the cell with some blackish strim on it, a small black mark with reddish-yellow centre below middle of cell, and a small black spot with reddish- yellow point on its lower extremity at lower angle ; a whitish postmedial patch striated with red-brown on costa and an elliptical patch between veins 4 and 1 ; the costal area towards apex striated with red-brown ; cilia dark red-brown with some white at tips. Underside of both wings with the ~rey areas suffused with red-brown. Hab. t~Eatl, Yahuarmayo, 1 ? type. Exp. 32 mm. XVIII.--Notes on British Forms of Apodemus. By MARTIN A. C. HINTON. TrHS paper contains an account of the results of a study of the long tailed field-mice collected in the Hebrides "for Mr. Ogilvie-Grant by Mr. W. R. Sbeppard in 1912, and by Mr. D. Anderson, Mr. P. D. Montague, and Mr. C. H. B. Grant in 1913. Several of the Hebridean forms have to be recognized as new subspecies of A. sylvaticus and A. hebri- dcnsis. In addition, a new subspecies of A. fridariensis, based upon material collected by Mr. Ogilvie-Grant in the Shetlands, is described. In his great paper on Mus sylvaticus the late Major Barrett-Hamilton remarks* that the possible range of the variations of this animal, "whether individual or geogra- phical, would seem to be narrow. Within this narrow range, however, variation is very evident and perplexing. The animal, indeed, while apparently having small power of varying, uses to tile utmost the power which it possesses." In working out the first collection from the Hebrides he and I were struck with the differences which exist between some of the insular races then examined, but lacking specimens from certain islands, since visited, and without a far more detailed investigation of the cranial characters than was then P. Z. S. 1900, p. 393. 118 Mr. M. A. C. IIinton on possible, we were unable to do more in our first paper than refer all the material to 21. syh, atict, s and notice the ten- dcney of certain of the island forms to approach .4. ]~ebri- densis of the Outer Hebrides. The skull-material obtained by the collectors named above and a carefully chosen series from other British localities have now been investigated. A long series of measurements were taken with the utmost care. The data so collected will, I hope, be published later elsewhere, but in the table at pp. 120-121 a summary consisting of the average relative values of the various dimensions in each British race is given. It is important to observe that in all cases, unless the contrary be stated, the measurements refer to thoroughly adult skulls in which the teeth are at least half-worn. ]t now appears that in practically every island of the tIebrides differentiation from the parent stock has proceeded so far that the most logical course would be to describe the mice of each island as distinct subspecies. On the mainland cf Britain the same process is seen at work. Skulls from the English plains taken here as being typical of 2t. s. sylva- ticus seem to be distinguishable from those of Wales or from the Scotch Highlands; those from the lowlands of Scotland in turn have their peculiar characters. But in order to define these mainland fbrms it will be necessary to have far more material of the right kind than is at present available. To quote Barrett-Hamilton once more, the work must be based upon averages, and not upon individuals, and it will require the most careful procedure. Apodemus sylvaticus, Linnmus. A. NoN-HEBaIDEAN BRITISH RACES. A. syh, aticus sylvaticus, L. Twelve old skulls from Kent, Essex, Middlesex, Oxford- shire, Gloucester, Leicester, and Suffolk, in which the condylo-basal length ranges between 22 and 23 6 mm., are treated as representative of this subspecies ; the average wdnes of the reduced dimensions, the condylo-basal length taken as 100, are given in the table at pp. 120-121. The Welsh skulls (c.-b. 1. 22'2-23"6) show a slight tcn- dcncy to become narrower and deeper, and more definite indications of shortening of the postmolar and diastemal lengths, accompanied by a decrease in the size of' tile bullm. Two types seem to occur in Scotland. In one, represented by skulls from Edinburgh, Lanark, and Dunphail~ ]~lgiu British f'orms of A1)ode,nus. 119 (c.-b. 1.23"2-23"5), which is not unlikely characteristic of the lowlands, the size is about as ill English s. sylvatictes. ]n this form the zygomatic, interorbital, and cranial widtils are relatively small, the brain-case more depressed, the post- molar ]engtb and bullm are smaller, while the nasals, rostrum, incisive foramina, and masseteric plate tend to be ~mrrower. The second or highland type is represented by the specimens ~- from Loeh Awe and Fortrose. These are rather small (e.-b. 1.22-23"4; 7 being 22'8 or less) ; their zygomatic breadth, though greater than in the "lowland" form, is relatively less than in England; the cranial width and depth are slightly increased; the palatal length is distinctly greater, the postmolar length, on the other hand, shorter, although the bulhe remain about as in England; the nasa]s arc rather larger, cspecially wider; the diastema and incisive foramina are slightly longer, the latter a little ~idcr ; the rostral breadth and the width of the masseteric plate arc about as in England. A skull from the mainland of Shetland (North Roe)¢ resembles the highland form in its small size, broad deep brain-case, and short postmolar length; but it differs in other respects. Although further material is necessary be{'ore the cxact status of this form can be determincd, it obviously represents A. sylvaticus, and is quite distinct from the large form inhabiting the neighbourmg island of' Mid Yell which is described below as a subspecies of ,4. fri- dariemis. Skulls from Jersey agree with the largcst English ones i,, size; their relative dimensions show increased zygomatic, interorbital, and cranial widths ; a deel)cr brain-case ; shorter postmolar length ; rather shor~ diastcma, with long and wide incisive foramina. In several of these respects tllere is agreement with the form of the Scotch highlands. The skull of the Alderncy form is considerably larger; iu its narrower and rather depressed brain-ease and less expanded zygomata it agrees with English or Welsh crania. All four skulls from Scilly are larger titan thc largest from England (c.-b. 1.23"8-2-k3) ; the biggest one is nearly equal to that from Ahlcrney. The zygomatic and inter- orbital breadths are small ; the brain case is as narrow but not quite so deep as in Wales ; the postmolaL" length is as in I have to thank Mr. C. H. Alston, 5Jr. I[ugh St. Quiutln, and 5:Jr. Ogilvie-Grant for this material, t North Roe is at the northern end of the island; at Dmlrossness, at the southern end, a large form i,~ known to occur~ w]iich may turn out to be a form of fridariensis. Average (5"anial .~ylva- Apodemus sylvatieus. tieus. Channel Seotlal,d. , Islands. -fi 4 4 4 (12) (4 (3) (9) d. (2) (1) (4) I 1. ! 23,0 12"! 1333 22.6 22'4 23"55 24"4 24'0 100 100 100 IO0 100 l c';i 1:1:~8 10190: 1[0180~ .ol.q:9 11"5 110,'5 109"5 1109'66 L09"O 3. ,)575 548 52"8 54'6. 57"2! 5~ "35 55'0 34'12 5595 4.1 1773 1~-5 16'56 17"7 17"85 18 25 16 8 [7 2 1775 5. 49~;8 49'2 ]47'7 50"9 52'2 50"3 49"2 t9"25 50 6 6. 3402 35"17 32-56 35-43 36 1 35"45 3#4 34'45 34"8 7. / 47"25 46"77 46"26 46"45 t6'4 46"55 46"3 ~7"27 46 "25 .)72 27"0 27'5 26"97 270 : ;:: 22 :°2 i0"6 41'65 38'9 4092 39'55 I0. 11"89 11"52 10'83 12"14 11'6 11'67 12"3 11'87 123 11.; 53'94 53'8'~ 54'13 54"32 53'6 53'95 54'5 53,9 54"45 29"0 28'25 28'3 28"2 29'4 24-1 2425 238 22"6 233 lI. 7"3~ 7"72/ 6"86 7"77 8"05 8"27 7"4 6'87 8"42 7'0 778 8"04 1~ 120.28!19.8/~9~3 20.3~ 19'6 20"65 19"3 19.47 20"3 1965 19'11 19"43 16.1 1025 10"75[ 10-0 10.29 10'7 997 115 11'27 10"6 10'74 10'07 10"52 ~7 1564 / 1557 i 1~561 15~9 15"6 16'15 16'0 1594 16"0 15'831 16'33 16"25 Number in ( ) of skulls upon which averages are based.