62 SIRENIA. 



preponderance of the Marsupial Group in these Colonies, no 

 less than ninety-three species, exclusive of nine well-marked 

 varieties, belonging solely to the fauna of Australia and its out- 

 lying islands, while three (Macropus agilis, Dactylopsila trivirgata, 

 and Phalanger maculatus) are common to it and the Papuasian 

 or Austro-Malayan sub-regions ; the number of known Marsupials 

 being but one hundred and fifty-one, with twelve recognizable 

 varieties, it therefore follows that Australia possesses almost two- 

 thirds of the total. 



Order I.-SIRENIA. 



Head rounded, not disproportionate in size as compared with 

 the trunk, from which it is inconspicuously separated by any 

 externally visible neck. Nostrils valvular, separate, placed above 

 the fore part of the obtuse truncated muzzle. Eyes very small, 

 with a well developed nictitating membrane. Ear without pinna. 

 Mouth small or moderate, with tumid lips beset with stiff bristles. 

 General form of body depressed and fusiform. No dorsal fin. 

 Tail flattened and horizontaly expanded. Fore limbs paddle- 

 shaped, the digits enveloped in a common cutaneous covering. 

 No trace of hind limbs. Skin wrinkled, rugose, naked, or with 

 fine hairs sparsely scattered over it. Clavicles absent. Pelvis 

 rudimentary. 



The Sirenians are inhabitants of bays, estuaries, lagoons, and 

 large rivers, in the shallow waters of which they find abundance 

 of the marine algse and fresh- water grasses on which entirely they 

 feed. They are as a rule gregarious, are slow and inactive in 

 their movements, and in disposition mild, inoffensive, and 

 apparently without much intelligence, for which latter reason they 

 are within a measurable distance of total extinction, being valu- 

 able for their flesh as food, and for their hides, but especially for 

 the excellent oil which is extracted from the thick layer of fat 

 immediately underlying the cuticle, as a fact they are already 

 becoming very scarce and difficult to obtain in all settled districts. 

 Members of the two existing genera, Manatus and Halicore, are 

 natives of the tropical shores of Eastern America and the "West 

 Indies, Africa, Asia, and Australia, but the genus Jthytina, from 

 Behring Straits, a much larger animal than either of the others, is 

 supposed to have been exterminated through the agency of man 

 within the last hundred and twenty-three years, but it is reported 

 (Nordenskiold, Voyage of the Vega) to have been seen in its 

 original home so late as 1854. 



During the Miocene and early Pliocene epochs Sirenians 

 abounded in the coastal waters of Europe and North America, 

 and a species has also been discovered in the nummulitic limestone 

 of the Mokattam Hills near Cairo. 



