THE ANCIENT MAMMALS OF BRITAIN. 319 



ossified tubular perforation running through the centre of 

 the beak. A species of the extinct Shark-toothed Dolphins 

 (Squalodon), together with a Killer ( Orca), Black-Fish ( GloUceph- 

 alui), Dolphin (Delphinus), and Bottle-nosed Dolphin (7'ur- 

 siops), completes the list of Crag Cetaceans. It may be added 

 that the Sirenians, that is to say the Order to which belong the 

 living Manati and Dugong, are represented by a skull of the 

 extinct genus Halitherium from the Red Crag, but it is quite 

 possible that this specimen may have been washed out of the 

 Miocene beds. 



Although the Fauna of the Crag would have appeared strange 

 and foreign even to an inhabitant of Britain during the early 

 historic period, when the Wolf, Bear, Aurochs, and Beaver 

 still lingered in our islands, could a cave-man have seen 

 Britain as it existed during the period of the Crags, he would 

 not have found the Fauna very different to the one with which 

 he was acquainted, Mastodons taking the place of Elephants, 

 and the Hornless Rhinoceros representing the Two-horned 

 Woolly species, which he had probably been accustomed to 

 hunt. 



III. The Lower Tertiary Period. 



Between the Coralline Crag and the Hempsted beds of the 

 Isle of Wight, which belong to the middle portion of the 

 Oligocene Period, and are the next Tertiary deposits met with 

 in Britain, is a long gap, owing to the complete absence of all 

 representatives of the Miocene and Upper Oligocene strata of 

 the Continent. In consequence nf this imperfection of the 

 record, instead of finding a gradual transition from the 

 Mammals of the Crag Period as we puss downwards through 

 the Miocene bed till we reach the Oligocene, we notice that 

 the Mammalian Fauna of the lower Tertiaries ot Britain is 

 utterly unlike that of the upper beds, and shows not the 



