78 MR. K. ANDERSEX ON BATS [May 16, 



species of the simphx-gron-p also the lower Pg is very much i-educed 

 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, invariahly, in the 

 tooth-row. 



The following I'emarks apply to Rh. simjjlex and Bh. megapliyllus, 

 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, in relation to p^ and p^ varies 

 indivichuilly (in the same geographical race, and in examples 

 from the same locality and of apparently the same age) : 

 completely in the tooth-i'ow (one specimen), or slightly towards 

 the external side (two), or half external (one), oi- almost quite 

 external (one), or completely external (one). This " vacillation " 

 in the position of pg 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 {Rh. aa^otis). — p* is 

 comparatively large, with a well- developed, pointed cusp. From 

 its base to its tip this cusj^ is directed ohliquely inioards, under an 

 angle of about 25° to 45" with the vertical line ; also in those 

 species of the present grouj) in Avhich 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 ividely 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 P3 is external in position, or even tvJien it is 

 completely/ lost, we still, rather often, find pg and p^ separated by a narrow inter- 

 space, reminiscent of the time when pg 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 w ill be strengthened ; and such cases are, in fact, not verj' rare : — rin some 

 individuals, and just those of the most primitive species of the genus {simplex, 

 megapliylhis, horneensis, refulgens, pliilippinensis), I find kn arrangement of the 

 upper teeth which can be graphically expressed as follows : cp pmhn-m^, i. e. the 

 anterior of the upper premolars in contact with the canine, the posterior in contact 

 with the first molar, but bettveen the two "p " still a narrow interspace, apjiarently 

 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 p"*. 



* Oa\y the following measurements require some explanation : — Ears, length from 

 base of inner margin to tip. Forearm, from posterior point of radius to front curve 

 of carpus (wing bent), therefore somewhat greater than the length of radius measured 

 on skeletons. Metacarpals, as far as possible the true lengtli of the bones. 2nd 

 phalanx, always exclusive of the cartilaginous " ird phalanx " (this restriction being 

 of especial importance in measurements of the 3rd finger, the terminal cartilaginous 

 rod of which is comparatively large). Hind foot, with claws. Skull, total length, 

 to front of canines (not to fi-ont 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 loiver teeth, exclusive of incisors. 



