22 



THE SEA-COWS. 



incisor is the only tooth in the whole set 

 which takes the place of .a milk-tooth. In the 

 female it is not developed. On the inner side 

 of this curved premaxilla the palate forms a 

 sort of narrow groove, which is continued 

 backwards to the posterior nares. Near 

 these openings there are in each half of the, 

 jaw large teeth with quite smooth, round or 

 oval grinding surfaces. The lower jaw is 

 very high, but short, and is cut away in front 

 in correspondence with the curve of the upper 

 jaw; and this abrupt and narrow portion, 

 which fits into the above-described groove of 

 the upper jaw, is covered by a rough, thick 

 horny plate, below which there are in the 

 bone four empty sockets from which the teeth 

 have disappeared. In the posterior horizontal 

 part of the jaw there is a varying number of 

 molars similar to those of the upper jaw. In 

 the milk-dentition there are five molars in 

 each half of the jaw, both above and below, 

 but these gradually get reduced to two. 



It is still doubtful whether the specimens 

 obtained in the Red Sea and those on the 

 coast of Australia belong to different species 

 or not. In any case these animals have the 

 same habits. They keep to the coasts, seldom 

 ascend the rivers, swim slowly, and allow 

 themselves to sink to the bottom like a lump 

 after coming to the surface to breathe, during 

 which process they show the upper part of 

 their body. Only in moments of danger do 

 they make use of their strength, which is 

 sufficient to enable them to deal vigorous 

 blows with their tail. The mothers keep 

 their young one pressed to their breast under 

 their flipper, defend it to the last, and allow 

 themselves to be killed rather than desert it. 

 The dugongs prefer bays that are not very 

 deep, where they find abundance of sea-weed. 

 They assemble in flocks where they find 

 themselves secure, migrate to fresh parts 

 when they have fully cropped a submarine 

 pasture, but always keep to the coasts during 

 these migrations. They are hunted for their 

 fat, for their hide, and for their tolerably 



palatable but rather sweet flesh. They are 

 either harpooned, as in the Red Sea, or are 

 caught in nets and being thus prevented 

 from breathing are actually drowned. 



The Manatees (Manatus) are distinguished 

 from the previous genus by their straight 

 head, thicker body, by having smooth nails 

 on the last phalanx of the four outer digits of 

 the flipper, and by having the tail rounded off 

 to the form of a thick disc. The jaws ex- 

 hibit only a faint indication of that very pro- 

 nounced curvature by which those of the 

 dugong are characterized. The incisors and 

 canines are both wanting in adults, but in 

 new-born animals some representatives of 

 these teeth are found, but these soon drop 

 out in the lower jaw, while a single pair of 

 incisors persist in the young animal, but after- 

 wards get lost. The sockets of these teeth 

 are covered, as in the dugong, by a callous 

 horny skin. The molars are never shed, but 

 are gradually developed one after the other 

 as the old ones get worn away by use. In 

 this way a dozen molars may be formed in 

 each half of the jaw, but there are never more 

 than seven or eight in use at one time. These 

 molars are similar in form to those of the 

 tapirs. They all have two or more roots, and 

 the almost cubical crown has on the chewing 

 surface two transverse ridges separated by a 

 deep groove. 



Two species of manatees are distinguished, 

 the smaller of which (Manatus senegalensis) 

 inhabits the coasts of West Africa and 

 ascends the Senegal and other rivers, while 

 the other larger species (M. australis), fig. 

 144, which attains as much as 10 feet in 

 length, is confined to the east coast of 

 America. This latter species has two geo- 

 graphical varieties, one in the north found all 

 round the Gulf of Mexico, the other further 

 towards the south 



The manatee of the Amazon ascends very 

 high into the interior of the mainland, as 

 high as the rapids. It is eagerly pursued in 

 the large rivers of Brazil and Guiana and 



