380 CETACEA. 



The blow-hole is externally single, and no trace of an 

 olfactory nerve can be distinguished. The anterior ribs 

 are more closely united to the vertebrae than in the 

 Mystacoceti ; the sternum (in the young animal at least) is 

 composed of several distinct segments, and it is attached 

 to several of the ribs. The cervical vertebrae are, usually, 

 nearly or quite free, but are sometimes completely united. 



The Odontoceti have been divided by Prof. Flower into 

 three great families ; namely, Physeteridoi, consisting of 

 the Cachelots and Ziphioid Whales ; Platanistidce, the 

 long-snouted fresh-water Dolphins of India and South 

 America ; and DelphinidcB, comprising the remaining 

 Dolphins, Porpoises, &c., along with the Narwhal and 

 the Beluga. Of these groups the first and third are 

 well represented in our fauna, while the second consists 

 exclusively of tropical forms. 



The Dugongs and Manatees of the tropics were formerly 

 placed in this order, under the name of Herbivorous 

 Cetaceans, but a better acquaintance with their organiza- 

 tion has led to their separation as a distinct order, Sirenia, 

 holding a close relation to the hoofed animals or Ungidata. 



One or two specimens of the Manatee of the West 

 Indies {Manatus australis) have been cast ashore on our 

 islands, and the species has therefore been claimed as 

 British, but as the animals were dead and even putrid, 

 and had probably been drifted by the Gulf Stream from 

 a great distance, it can have no claim to be regarded as a 

 member of our fauna. 



