52 CLASS I. MAMMALIA, ORDER IX. MARSUPIALIA. 



fice of the nostrils, from whence it is ejected, with consider- 

 able force, through a small aperture, called the blowhole, on 

 the upper part of the head. In some of the whales, as in the 

 great Balaena, beside this arrangement, the mouth is fur- 

 nished with rows of whalebone on each side, extended in the 

 form of thin plates, and terminating at their edges in fibres 

 or a sort of fringe, which serve the purpose of a sieve, or 

 strainer, to retain the large shoals of little animals that are 

 taken in with the water, whilst the water passes through and 

 escapes. 



The Balaena mysticetus, or great Greenland Whale, is an 

 enormous animal, which attains to a length varying from sixty 

 to seventy or eighty feet, and is nearly of as many in cir- 

 cumference. Its jaws are capable of being stretched twenty 

 feet apart, and its plates of whalebone are sometimes twelve 

 feet in length. It is covered, under the skin, by a layer of 

 fat, which is often several feet thick, and yields, according to 

 the different sizes of the animal, from twelve to twenty tons 

 of oil. It used formerly to frequent the Atlantic coasts of 

 Europe and America; but to such an extent has the pursuit 

 of it been carried, that it has gradually been driven into the 

 recesses of the northern seas. 



\ There are other whales equal in length to this, but less val- 

 uable on account of their smaller circumference, their com- 

 parative leanness, and the difficulty of taking them. 



The Spermaceti Whales are without the whalebone, and 

 are remarkable for the disproportionate size of their heads. 

 This size is owing to the existence of certain cartilaginous 

 cavities upon their upper part, in which is contained the pe- 

 culiar substance known by the name of spermaceti. These 

 cavities are entirely distinct from that containing the brain, 

 which is very small. They have little fat in other parts of 

 their bodies ; and it is on account of the spermaceti only that 

 they are a valuable object of fishery. ' The odorous substance 

 called ambergris, appears to be a concretion formed in the 

 intestines of these whales, particularly when they are the sub- 

 jects of disease. 



IX. Marsupialia. The Marsupial animals have usually 

 been distributed among those orders of the class Mammalia, 

 to which they bear, in some particulars, the closest resem- 

 blance. Thus the Kangaroo has been enumerated among 

 the Rodentia, because it resembles them in its teeth, and the 

 length and strength of its hind legs. The Opossum has been 

 ranked among the Carnivora, and the Ornithorhynchus among 



