7o8 



MAMMALIA. 



Some Eocene fossils, known as Zeuglodonts, are regarded 

 by some (Lydekker, Dames) as primitive Cetaceans — 

 Archaeoceti — less specialised than modern forms, but Prof. 

 D'Arcy Thompson has advanced strong arguments in favour 

 of their affinities vfith Pinniped Carnivores. 



In regard to the possible affinities of the Cetacea, Sir 

 Wm. Flower maintains (i) that the hypothesis of their 

 descent from Ichthyopterygian reptiles is untenable, (2) 

 that they are separated from an alliance with Carnivora by 



Fig. 261. — Vertebra, rib, and sternum of Balo^noptera, 

 (From specimen in Anatomical Museum, Edinburgh.) 



C"". , Centrum ; n.a., neural arch ; n.sj^.. neural spine ; t./-.. trans\erse 

 process ; A"., rib ; St., sternum. 



many essential characters, (3) that they exhibit several, 

 though by no means close, affinities with Ungulata. 



The same authority refers to several facts which suggest 

 that, in their transition from terrestrial to marine life, the 

 Cetaceans may have passed through a stage in which they 

 lived in fresh water. 



[Table. 



