102 
Columbia (Ashcroft, 14; Kamloop3, 6; Okanagan, 12; Vernon, 2), but 
records only 5 skulls as being used for his fable of comparative measure- 
ments. 1 
In measuring 55 adult skulls of P. lordi in the National Museum of 
Canada, from British Columbia, the writer has found the interparietals 
very variable, the ratio of width to condylo-basal length of 24 males being 
25*3 (28- 6-20-0), and of 31 females 25*5 (28- 1-23 -7). The use of this 
ratio as given in the key is thus found to be of little value in determining 
individual specimens, nor does it seem tenable as a basis for separating 
groups of species or subspecies. 
The eleven available specimens of P. laingi were taken within three 
days ( August 29 to 31) and, consquently, show no seasonal differences. 
A nearly grown juvenile is coloured substantially like the adults, and four 
younger specimens have a soft, slaty blue appearance similar to juvenile 
Peromyscus specimens of the same age. The juveniles of different age 
seem to show that at least two litters of young are produced in a season. 
Perognathus parvus (Peale) is said by Osgood 2 to show dichromatism which 
is evidently not due to age, sex, or season. For comparison, six Oregon 
specimens of P. parvus were obtained on loan from the United States 
Biological Survey (two of the grey phase, Nos. 222285 and 222287, taken 
at Voltage, Sept. 10 to 13, 1916; four of the ochraceous phase, Nos. 57103, 
57107, 57111, taken at the Dalles in November, 1893; and one, No. 206709, 
at Willows in April, 1915). The colour differences were found to be slight 
but distinguishable, the grey phase resembling P. lordi in colour, but the 
ochraceous phase being yellower than the British Columbia specimens. 
Our series of sixty-four British Columbia specimens of P. 1. lordi 
show great uniformity in colour of specimens taken at the same season, 
but thirty spring specimens, taken on both sides of Osoyoos lake in May 
and early June, are considerably more ochraceous than twenty-three 
specimens taken in late August and September, the latter having a pale 
slaty appearance. A series of eleven specimens, adults and juveniles, 
from vicinity of Keremeos (Ashnola creek, 1,500 feet altitude, and Paul 
(Terebasket) creek, 1,350 feet altitude) in latter part of June and early 
July, have a slightly different appearance, being in thin, short-haired 
moulting pelage, very pale greyish in colour with a faint buffy tinge. There 
appears to be no approach to dichromatism in any of the lordi specimens, 
the changes in colour being entirely seasonal and caused by shedding, 
growth of new hair, and fading. Late spring specimens still in the winter 
coat show no apparent sign of wear or abrasion, and Mr. Laing states 
that the pocket mouse in southern British Columbia is not much in contact 
with vegetation and does not ramble through runways like Mierotus. A 
series taken by William Spreadborough at Osoyoos lake in 1905 show no 
more signs of fading than the series taken in the same region by H. M. 
Laing in 1928 and 1929. 
In size and general colour characters P. 1. lordi (Gray) seems inter- 
mediate between the small, pale ochraceous P. p. parvus (Peale) and the 
large, blackish P. laingi , whereas in certain cranial characters laingi 
1 Ibid., p. 62, 
*Ibid, pp. 34, 36. 
