78 MR. K. ANDERSEN ON BATS [May 16, 
species of the simplea-group also the lower p, 1s very much reduced 
in size and on the point of being driven out of the tooth-row, to 
the external side; in all the more primitive species of the group 
also the upper p* is reduced in size, but still, trnvariably, in the 
tooth-row. 
The following remarks apply to RA. simplea and Rh. megaphyllus, 
the dentition of these two species, the most primitive within 
the present group, being practically exactly alike :—p, very small, 
but decidedly less reduced than in the other species of the group. 
The position of this tooth, m relation to p, and p,, varies 
individually (in the same geographical race, and in examples 
from the same locality and of apparently the same age): 
completely in the tooth-row (one specimen), or slightly towards 
the external side (two), or half external (one), or almost quite 
external (one), or completely external (one). This “ vacillation ” 
in the position of p, is of some interest as being the first indication 
of a tendency towards driving this premolar out of the tooth-row, 
a tendency gradually increasing in a long series of more highly 
developed species, and culminating in the forms in which the 
tooth is quite lost, even in young individuals (4h. acrotis).—p? is 
comparatively large, with a well-developed, pointed cusp. From 
its base to its tip this cusp is directed obliquely mwards, under an 
angle of about 25° to 45° with the vertical line; also in those 
species of the present group in which the cusp is so much reduced 
as to be scarcely perceptible without a lens, it is invariably point- 
ing obliquely inwards, only to a still higher degree. The upper 
canine and p' always widely separated. In some individuals there 
is a very narrow interspace between p* and p’, on either side of the 
jaw, or on one side, no doubt a remnant of the place where p’, 
lost in all existing species, was situated (see footnote on p. 77). 
Measurements *, On p. 80. 
of the lower jaw. (2) When the lower p; is external in position, or even when it is 
completely lost, we still, rather often, find p, and p, separated by a narrow inter- 
space, reminiscent of the time when p; had its normal position in the tooth-row; if 
we can find, sometimes at least, a similar “atavism” in the upper jaw, our sup- 
position will be strengthened; and such cases are, in fact, not very rare :—in some 
individuals, and just those of the most primitive species of the genus (simplex, 
megaphyllus, borneensis, refulgens, philippinensis), I find an arrangement of the 
upper teeth which can be graphically expressed as follows: cp pm!m?mn®, 7,e. the 
anterior of the upper premolars in contact with the canine, the posterior mm contact 
with the first molar, but between the two “p” still a narrow interspace, apparently 
a remnant of the place where the lost premolar was situated; if so, however, the 
lost p is, of course, p%, those present p? and pt. 
* Only the following measurements require some explanation :—Hars, length from 
base of inner margin to tip. Forearm, trom posterior point of radius to front curve 
of carpus (wing bent), therefore somewhat greater than the length of radius measured 
on skeletons. Metacarpais, as far as possible the true length of the bones. 2nd 
phalane, always exclusive of the cartilaginous “3rd phalanx” (this restriction beg 
of especial importance in measurements of the 3rd finger, the terminal cartilagmous 
rod of which is comparatively large). Hind foot, with claws. Skull, total length, 
to front of canines (not to front of premaxilla). Width of brain-case, above root of 
zygomata. Supraorbital length, distance between point of junction of supraorbital 
crests with sagittal crest and median anterior point of nasal swellings. Mandible, 
condylus to front of incisors. Upper and lower teeth, exclusive of incisors. 
