206 



MAXATIDJE. MAMMALIA. MANATID.E. 



of ribs. One of the most interesting visceral modifica- 

 tions is that of the heart (fig. 82), which may be said 

 to have two apices, seeing that the ventricles are par- 

 tially separated from one another, and independent at 

 then: lower ends. In the annexed cut the letters of 

 reference indicate as follows : a, right auricle, b right 

 ventricle, e, pulmonary artery, d, left auricle, e, left 

 ventricle, f, the aorta. In most particulars the skeleton 

 strictly conforms to the cetacean type ; but in the head 

 and neck we notice several departures, the cervical 



I 



Heart of the Dugong (llalicore Dugong). 



vertebrae remaining quite distinct, whilst the head is 

 shortened and comparatively massive in some species. 

 In the Dugong Plate 34, fig. 139 the intermaxillary 

 bones are enormously developed for the implantation 

 of its incisive tusks, whilst the lower jaw is remarkably 

 broad and deep. These cranial peculiarities are not 

 present in other allied genera. The several bony 

 elements of the fore-limbs are more perfectly formed 

 than in the zoophagous cetaceans, the would-be posi- 

 tion of the hinder extremities being indicated by an 

 attenuated V-shaped bone, constituting a rudimentary 

 pelvis. True V-shaped bones also exist along the 

 hoamal aspect of the caudal vertebrae. In conclusion, 

 we have only to observe that all the Manatidse are 

 found near the sea-coast, and near estuaries and mouths 

 of' rivers, up which they occasionally wander to a con- 

 siderable distance, feeding on marine fuci and other 

 kinds of aquatic vegetation. 



THE MANATEE (Manatus australis) Plate 36, 

 fig. 84 is an inhabitant of the shores and great open 

 rivers of the South American continent, being particu- 

 larly abundant off the coasts of Guyana and Brazil, 

 where it is commonly known as the Sea-cow. The 

 term Lamantin is sometimes applied to it as well as 

 to another species. The Manatees are gregarious in 

 their habits, and like other Cetacea are devotedly 

 attached to their young, which they defend with great 

 vigour. In the adult state the skin presents a greyish- 

 black colour, whilst, in common with other species of 

 the same genus, the flippers are each provided with 

 four flattish nails, that of the thumb being wanting. 

 They have thirty-two molar teeth, that is, eight on 

 either side above and below, their crowns being irregu- 

 iarly flat, square-shaped, and' divided transversely by 



ti central groove. There are no canines or incisors 

 except in extremely young individuals. Under ordi- 

 nary circumstances the habits of the Manatee are mild 

 and inoffensive. It is readily taken with the harpoon, 

 and is chiefly valued on account of its flesh, which is 

 stated to be excellent eating. Though formerly very 

 plentiful, the Sea-cow hunters have greatly reduced 

 their numbers. When these animals raise the anterior 

 half of the body out of the water, they display a fanci- 

 ful resemblance to a human figure, and this circum- 

 stance induced our ancient navigators to believe in the 

 existence of sirens, mermen, and mermaids. 



Two other species of the genus Manatus are also 

 known the Lamantin, properly so called (M. Sencgal- 

 ensia of Adanson), which is a native of the western 

 coasts of tropical Africa, and the Mexican Sea-cow (M . 

 latirostris), a very large species, upwards of fifteen 

 feet in length, found on the shores of Florida, Mexico, 

 Surinam, and some of the West Indian islands. 



THE INDIAN DFGONG (Halicore Dugong) Plate 26, 

 fig. 85 is a species of very considerable interest, though 

 much smaller than the foregoing, seldom measuring more 

 than seven or eight feet from the tip of the abrupt and 

 flattened snout to the end of the broad crescentic tail. 

 On turning to the drawing given at Plate 26, fig. 85, 

 it will be seen that the flippers are not furnished with 

 nails, but then- margins are thickened and tuberculated. 

 One of the most characteristic features of this animal 

 arises out of the presence of two large incisors or tusks 

 in the upper jaw, a ( fig. 83), the molars being flat, and 

 varying numerically from eight or ten to twenty, ac- 

 cording to age and other circumstances. " In the female 

 Dugong," says Professor Owen, " the growth of the per- 

 manent incisive tusks of the upper jaw is arrested before 

 they cut the gum, and they remain through life con- 

 cealed in the premaxillaries. The tusk is solid, is 

 about an inch shorter, and less bent than that of the 

 male; it is also irregularly cylindrical, longitudinally 



Fig. 83. 



Skull of the Indian Dugong (Halicore Dngong). 



indented, and it gradually diminishes to an obtuse 

 rugged point. The base is suddenly expanded, bent 

 obliquely outwards, and presents a shallow exca- 

 vation." Speaking of other peculiarities, the samo 

 authority also observes that the external form of the 

 Dugong is " not so well calculated for moving rapidly 

 through the water as that of the dolphin and other 

 carnivorous cetacea, which subsist by a perpetual pur- 



