RECENTLY DISCOVERED TERTIARY VERTEBRATA OF EGYPT. 303 



higher in the crown. In Elephas pr{?mgenius there may be as many 

 as twenty-seven ridges in the last mohir. All this long series of 

 changes is illustrated by specimens shown in the paleontological gal- 

 leries of the Natural History Museum, London, and representing, per- 

 ha]3S, the most complete history of any mammalian group yet knowm. 



In the Upper Eocene beds the Hyracoidea are represented by two 

 genera, Megalohyi^ax and Saghatherium^ including several species. 

 Xone of these throw any light on the relationships of the order; but 

 some of them are of large size and indicate that formerly the group 

 was of far greater importance than it is to-day, w^hen its only represent- 

 atives are a few comparatively small species, all of which, according 

 to some authorities, should be placed in a single genus, Procavia 

 (Hyrax). 



The occurrence of remains of Sirenians in the Middle Eocene beds 

 of Egypt has long been known, Owen having described — under the 

 name Eotherhim — a brain cast of one of these animals from the 

 Mokattam Hills, near Cairo, so long ago as 1875, and further remains 

 from the same locality were noticed by Filhol in 1S7S. AVithin the 

 last four or five years not only have skulls and other portions of 

 Eotherhim been found, but remains of other genera have come 

 to light, both from the IMokattam Hills and from the somewhat later 

 deposits of tlie Fayum. These early forms have been described by 

 Dr. O. Abel and the present writer. Their chief points of interest 

 are those in which they show approximation to the land mammals 

 from W'hich the group arose. Thus in Eotherhim, the pelvis has a 

 complete obturator foramen inclosed by the pubis and ischium, and, 

 judging from the acetabulum, there must have been a fairly w^ell- 

 developed hind limb. In the later forms, even at the top of the 

 ]\Iiddle Eocene, the jDelvis has undergone considerable further reduc- 

 tion, the pubis and ischium not inclosing a foramen and the 

 acetabulum being so small and indefinite that the hind limb must 

 have been rudimentary. In these early Sirenians also the dentition 

 approaches the primitive Eutherian type, there being three incisors, a 

 canine, four premolars, and three molars on each side of the upper 

 jaw. In the later types there is at most one pair of incisors, often 

 much enlarged, while the canines and some of the premolars also are 

 lost. This more normal structure of the pelvis and the character of 

 the teeth show that a Sirenian such as Eotherhim is not very remote 

 from the terrestrial ancestor from which the group must have sprung; 

 and it is very interesting to note that in the form of the pelvis and 

 of the teeth this ancestral form must have much resembled Moeri- 

 therhim., a fact strongly supporting Blainville's suggestion that the 

 Sirenia and Proboscidea are closely related. Many other points of 

 similarity might be pointed out, such as the form of the brain in 

 Mceritheriwn and in Eosiren or Eofherh/m,, and modern representa- 



