178 MAMMALIAN DESCENT. [LECT. VII. 



vessels and nerves, and the notches and ridges that are 

 in all skulls; all the sutures are filled in with bony 

 matter. Yet, whilst thus agreeing with the Bats in the 

 complete ankylosis or union of the cranial elements, they 

 have disappointed me in not yielding what I expected to 

 find, namely, a correspondence, in form, with the skull 

 of the " Pteropinse," or frugivorous Bats. They come 

 nearest in size to, and the largest of them are fellow- 

 countrymen with, the Colugo, but skulls of both types 

 placed side by side show only the ankylosis, and the 

 general characters, in common. As they live a similar 

 life, I expected to find the tympanum, or ear-drum, 

 similar in both, but that cavity, in Bats, is developed 

 much more in the fashion of that of the Tupaia, and of 

 a kind, next to be described, from Zanzibar, and not like 

 what is seen in the Colugo. In the lesser embryo of 

 Galeopithecus, the annulus, or drum-ring, is a strong, 

 thin, flattish dish of bone ; afterwards, in older speci- 

 mens, I find no bulla, or additional swollen part, either 

 in bony or cartilaginous tracts; but one thing I do find, 

 namely, that the bony tract soon creeps along the 

 meatus externus, or outer passage ; quite an unusual 

 thing in an Insectivore; in Mammals higher up, this 

 is constantly seen. In Galeopithecus even this is done 

 in a strange manner; for the squamous bone grows 

 strongly downwards in front of the meatus, or passage, 

 by its post-glenoid process, and behind that passage by 

 the downward s^g from its hinder part, the great 



