| OCR Text |
Show 78 MR. K. ANDERSEN ON BATS [May 16, species of the simplex-gvoup also the lower p3 is 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 p2 is reduced in size, but still, invariably, in the tooth-row. The following remarks apply to Rh. simplex 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 tbe group. The position of this tooth, in relation to p., and pt, 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 p3 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. acrotis).-p2 is comparatively large, with a well-developed, pointed cusp. From its base to its tip this cusp is directed obliquely inwards, 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 pointing obliquely inwards, only to a still higher degree. The upper canine and p4 always widely separated. In some individuals there is a very narrow interspace between p2 and p‘, on either side of the jaw, or on one side, no doubt a remnant of the place where p3, 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 when it is completely lost, we still, rather often, find p., and p4 separated by a narrow interspace, reminiscent of the time when p:i had its normal position in the tootli-row; if we can find, sometimes at least, a similar " atavism" in the upper jaw, our supposition 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 pmhn-m3, i. e. the anterior of the upper premolars in contact with the canine, the posterior in 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, p3, those present p- and p4. # Only 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 length of the bones. 2nd phalanx, always exclusive o f the cartilaginous " 3rd phalanx " (this restriction being of especial importance in measurements of the 3rd finger, the terminal cartilaginous rod of which is comparatively lar<?e). Sind foot, with claws. Skull, total length, to front of canines (not to front of premaxilla). Width o f 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. |
