1902.] VERTEBRATES FROM UPPER EGYPT. 229 



orbits. The teeth were of a very remarkable type ; each of 

 the molars consisting of two transverse ridges united internally 

 with the continuous inner wall of the tooth, so that the molar as 

 a whole somewhat resembled a reversed molar of a Rhinoceros 

 The dental formula seemed to have been I. 1, Pm. 3, M. 3, in 

 both upper and lower jaws. The affinities of this animal were 

 quite uncei^tain, but the limb-bones which seemed to belong to it 

 indicated relationship with the Proboscidea, of which it may have 

 been an early but highly specialized offshoot. 



Another peculiar mammal was Phiomia serridens, of which 

 the anterior part of the mandible was the type. In this animal 

 there was a single pair of very large procumbent incisors with 

 a peculiarly serrated outer edge ; behind this there was a long 

 edentulous diastema, much as in the Rodents, then came a small 

 premolar and a large molar similar to the carnassial of some of 

 the Carnivora. The relationships of this creature were likewise 

 quite uncertain : it had been suggested that it might be a peculiarly 

 modified Creodont, but it possessed some characters that seemed 

 to point to the Diprotodont Marsupials, and even to the Multi- 

 tuberculata. Further material would be necessary before the 

 question could be settled. An early member of the Hyracoidea 

 and a gigantic land-tortoise allied to Testudo perpiniana, also 

 found by Mr. Beadnell, were likewise referred to. 



The fui'ther remains of Mceritherium and PalcEomastodon 

 collected fully confirmed the position ascribed to these genera as 

 early forms of the Proboscidea. Of Palceomastodoii the upper 

 and lower dentitions were now fully known, with the exception of 

 the front teeth of the upper jaw. The dental formula for the 



3 3 



cheek-teeth was : — Pm. ^, M. -. The single lower pair of incisors 



were procumbent and in contact in the middle line ; anterioily 

 they wore to a sharp edge. The upper incisors seemed to have 

 been compressed, downwardly-directed tusks, with enamel on one 

 face only. In the skull the jugal bone was large and extended 

 on to the face, not being merely a small bar of bone in the middle 

 of the zygomatic arch as in the Elephantidse. 



Dr. Andrews pointed out the great diiferences between the 

 Middle Eocene Mveritherium and the Upper Eocene Palmo- 

 mastodon, and suggested that the more rapid rate at which 

 evolution seemed to have proceeded in the earlier stages of 

 development of many groups of mammals might perhaps in some 

 cases be accounted for as follows : — 



" Among the Ungulates, at least, the earlier members of a group 

 " are usually of small size, and as specialization advances an 

 " increase in bulk also takes place ; a well-marked instance of this 

 " may be seen in the line of descent of the Horse, and there are 

 " many other cases. This increase in bulk must, in most cases, 

 "involve a lengthening of the individual life, which is often 

 ' indicated in the gradually increasing hypselodonty of the teetli, 

 " implying an increased pex'iod of efficiency. ¥7hen the length 



