308 



CHAPTER XLL 



ORDERS OF MAMMALIA (Continued). 

 SiREXIA AND CeTACEA. 



Okder IV. Sirenia. — This order comprises no otlier living- 

 animals except the Dngongs and Manatees, which are often 

 placed with the true Cetaceans (Whales and Dolphins) in a 

 common order. There is no doubt, in fact, but that the 

 Sirenia are very closely allied to the Cctacea, and though 

 they are to be regarded as separate orders, yet they may be 

 advantageously considered as belonging to a single section, 

 whicli has been called Mutilata, from the constant absence 

 of tlie hind-liml)S. 



The Sirenia agree with the Wliales and Dolphins in their 

 complete adaptation to an aquatic mode of life (fig. 616); 



Fig. GIG — Side-view of young Monatus Aincricmnts, greatly reduced in size; n, Nostrils. 

 (.A.fter Murie.) 



especially in the inesence of a 'powerful caudal fin, tvJiich 

 (lifers from that of Fishes in hchig flaccd horizontcdly and in 

 hcing a mere expansion of the integuments, not supported hy 



