204 TERTEBRATE AlflMALS. 



said to be very palatable and wholesome. The Dugongs (Fig, 

 145) differ little in appearance and habits from the Manatees. 

 They are found on the coasts of the Indian Ocean and the 

 north coast of Australia, and are often killed and eaten. They 

 attain a length of from eighteen to twenty feet. The bones 

 of the skelebon are remarkable for their extreme hardness and 

 density. 



ITiG. 145. — Sirenia. The Dugong (Jlolimre, Indiaus). 



Besides these living forms, the Sirenia were represented 

 by a gigantic species which formerly inhabited Behxing Island 

 on the coast of Kamtchatka. This animal was described by a 

 M. Steller who accompanied Behring on his second expedition, 

 and he named it Rhytina. This enormous animal attained a 

 length of twenty-five feet, and a circumference of twenty feet, 

 and it appears to have been completely exterminated, no spe- 

 cimen having been seen for two centuries. 



Oedbr V. Cbtacba (Gr. letos, a Whale). — This order 

 comprises the Whales, Dolphins, and Porpoises, and it is 

 characterized by the complete adaptation of its members to a 

 watery life. The body is completely fish-like in form, the fore- 

 limbs are converted into svnmming-paddles, and the hind- 

 limbs are completely wanting ; while the hinder end of the 

 ))ody forms an extremely powerful, horizontal caudal fin. 

 Sometimes there is a dorsal fin as well. The nostrils may be 

 single or double, but always are placed on the top of the head, 

 constituting the "blow-hole." The body is very sparingly 

 furnished with hairs, or is wholly without them in the adult. 

 The head is generally of disproportionately large size as com- 

 pared with the body, and is rarely separable from the trunk 

 by any distinct constriction or neck. There is no sacrum, a,nd 

 the pelvis is only represented in a rudimentary form. Lastly, 

 the adult is either wholly destitute of teeth, or possesses only 



