678 SCIENCE PROGRESS 



which the group arose. Thus in Eotherium the pelvis has 

 a complete obturator foramen enclosed by the pubis and ischium, 

 and judging from the acetabulum there must have been a fairly- 

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

 of the Middle Eocene, the pelvis has undergone considerable 

 further reduction, the pubis and ischium not enclosing 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 EotJierium 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 Mceritherium, 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 Moeritherium 

 and in Eosircn or Eotherium, and modern representatives of 

 the two groups also agree in a number of points. Thus in both 

 there are (i) pectoral mammae; (2) abdominal testes; (3) bilo- 

 phodont molars, with a tendency to the formation of additional 

 lobes behind ; (4) the same arrangement of the intestines, and 

 (5) to some extent the same character in the placenta. Alto- 

 gether there seems to be very good reasons for regarding the 

 Proboscidea and the Sirenia as offshoots of a common stock, 

 the one being adapted for a terrestrial, the other for an aquatic 

 mode of life. 



All the carnivora collected belong to the primitive group, 

 the Creodonta, and all the species can be referred to genera 

 already known from Europe or North America. A few of the 

 limb-bones found seem to indicate that some of these animals 

 had adopted a semi-aquatic mode of life, and it is possible 

 that the Seals originated from some such type. 



Far more interesting than the Creodonts themselves is a 

 group that is now definitely known to have originated from 

 them, namely, the Zeuglodonts, usually — and probably rightly — 



