Mr. G. R. Waterhouse on the Classification of Mammalia. 409 



cause it has the flank membranes extended from limb to limb, 

 which enable it to sustain itself to a certain extent in the air, 

 but because in its dentition, more especially in the structure of 

 the molar teeth, there is a great resemblance to the ordinary 

 Vesper tilionid(2. The higher Quadrumana are remarkable among 

 Mammals for the possession of a perfect bony socket for the eye, 

 as in man ; but as we descend in the Quadrumanous group the 

 socket becomes less perfect; the malar bone, which forms the outer 

 and part of the lower boundary of the orbit, is at first produced 

 backwards, and joins with the sphenoid, superior maxillary and 

 frontal bones to form a complete socket for the eye : this cha- 

 racter runs through the whole of the old and new world Monkeys 

 with slight modifications only, indicative of a receding from man. 

 In Tarsius spectrum"^ the socket is still comparatively perfect as 

 compared with other Lemurid<2, where the orbital process of the 

 frontal bone, joined with the malar bone, merely forms a broadish 

 ring forming the outer boundary of the orbit. Lastly, in Galea- 

 pithecus we find the orbital process of the malar and frontal 

 bones unconnected; there is indeed a considerable hiatus be- 

 tween the two processes. Here, again, we find an approach to 

 the Bats : in these animals the orbital processes are generally 

 wanting, but in the Pteropi those of the frontal bones are much 

 produced; and so far, as well as in the general form of the skull, in 

 having more perfect hands than other Bats, and in their frugivo- 

 rous diet, they evince the nearest relationship observed in this 

 group to the Lemurida ; but there is no gradual blending of the 

 two groups. The dentition of the Pteropi is most unlike that of 

 Galeopithecus : the resemblance existing between the molar teeth 

 of the latter animal and the Bats, before alluded to, holds good 

 with the Bats generally, with the exception of the Pteropi. 



Among the Insectivora is a genus (Tupaia) which has a skull 

 and dentition remarkably approximate to that of the Lemurs. In 

 the Insectivora generally the zygomatic arch is but little de- 

 veloped or is incomplete, and there is no orbital process ; but in 

 Tupaia the zygomatic arch is well developed, and the malar and 

 frontal bones join to form a complete though slender bony orbit : 

 the latter bone (the malar) is remarkable for being perforated, a 



* In the Tarsius, an approacli to that extraordinary animal the Aye-Aye 

 may be perceived in the superior development of the two foremost incisors 

 of the upper jaw. The canines are very small compared with the ordinary 

 Lemuridcs ; and it is in tlie loss of these teeth and the other incisors (which 

 are minute in Tarsius), and some of the false molars, which produce in the 

 Aye-Aye so strong a resemblance (as regards the condition of the teeth) to 

 the Rodentia as to have induced Cuvier and others to place it in that order. 

 De Blainville has most ably combated this opinion and shown the true re- 

 lations of the animal in question, and has not omitted to notice this fact, 

 which had struck me, however, before I had seen his paper. 



Ann. ^ Mag. N. Hist. Volxn. 3F 



