INTJJODUCTTOX. 
xxni 
from tlie Crcodonts to the true Zeuglodonts. In the earliest type, Vrotocetus, tlie 
skull is already practically that of a Zeuglodont, the rostral {)ortion being, in fact, even 
more elongated than in some of the later forms ; at the same time, however, the 
opening of the nares is situated nearer to the end of the snout. The teeth are most 
remarkable; the incisors are not known, but the rest of the dentition is practically 
that of a typical Creodont, none of the teeth having assumed the peculiar serrated 
form characteristic of the later Zeuglodons. The canine is large, with a single 
though grooved root ; the first premolar is much smaller, the second large and 
two-rooted, the third and fourth have posterior cusps and are supported by three 
roots; the molars, which are small, are also three-rooted. In Prozenglodon (p. 243) 
from the later Birket-el-Qurun series the skull is likewise essentially Zeuglodont, 
though the external nares have shifted a little further back. The canine is much 
larger than the teeth before and behind it, and although the third and fourth 
premolars and the molars have serrated crowns, as in the later Zeuglodons, they, or at 
least the premolars, retain their inner buttress supported by a third root, so that in 
tooth-structure this genus is exactly intermediate between Protocetus and Zeuglodon. 
Fraas ( 29 ) has lately described still another annectant form, Eocetus, from about the 
same horizon as Prozeuglodon, which attained a very large size ; the skull approaches 
that of Zei(glodon in the position of the nares, but the teeth are Creodo.nt-like and 
possess inner (third) roots. Eemains of Zeuglodon itself seem to have been found 
in the same deposits as these intermediate types, but that genus continued to exist 
in the Qasr-el-Sagha beds above after they had disappeared. 
The Birds are represented in these beds by one or two fragments only, but those of 
considerable interest, because they show that most likely a true Batite {Emnopezus) 
existed in this district in the Upper Eocene period. This is of importance, because 
it indicates that possibly some at least of the main subdivisions of the Eatitte may 
have had a common ancestry in the Ethiopian region. If so, this would account for 
the likeness between the iEpyornithes and Struthiones referred to by Burckhardt, and 
also suggests the possibility of the relationship between these groups and the South- 
American Eheas. It is, of course, just possible that this genus is merely another 
instance of the results of retrogressive modification leading to loss of flight and 
increase in size in some group of Carinate Birds, such as has occurred in the case of 
the Gastornithes and Stereornithes ; in any case, much more material is required 
before any final conclusion can be reached as to the precise position of this genus. 
The Eeptiles are represented by members of the orders Crocodilia, Chelouia, and 
d2 
