Page:The American Cyclopædia (1879) Volume VI.djvu/309

 DUGONG 301 which fall and are not succeeded by permanent ones. The molars in the adult are fif, simple and elliptical, in the young |zf, far back on the horizontal portion of the jaw ; the grinding surface presents an outer rim of enamel, with the central ivory portion slightly depressed; they have no proper roots, and grow as long as they can be of use to the animal. The skin is thick and smooth, with a few scattered bristles ; the color is bluish above and white beneath ; 'the mammaj are two, and pectoral ; the fins are used not only for swimming, but for crawling along the bottom. The cranial bones are dense and large, with loose connec- tions where any sutures exist. The intermax- illaries are very large, extending back as far as the middle of the temporal fossas, and bent down at a right angle over the symphysis of the lower jaw, terminating nearly on a level with its lower margin ; this is necessary for the accommodation of the incisors, one of which is in each intermaxillary ; for this rea- son also the nostrils are displaced upward, dif- Dugong. ferent from the allied manatee, so that their opening is turned up as in the typical cetacea ; indeed, this animal comes nearer than its con- gener to the whales in its forked tail, absence of nails, and superior opening of the nostrils. The whole skull (and especially the frontal bones) is comparatively short ; the parietal crests are widely separated ; there is no bony tentorium, no sella turcica, very few and small openings in the cribriform plate of the ethmoid bone, and the optic foramina are converted into a long and narrow canal. The lower jaw corresponds to the angle of the intermaxilla- ries, and is bent downward at the symphysis ; on its anterior surface are three or four rough and shallow alveoli, sometimes containing ru- dimentary incisors. The cervical vertebra are 7, separate; the dorsals 18, with spinous pro- cesses bent back and elongated from the first to the last, and of the same length as the transverse; the lumbar 8, with long spinous and transverse processes ; one sacral, to which rudimentary pelvic bones are suspended ; cau- dals about 24, with chevron bones for the ante- rior three fourths, and becoming flattened pos- teriorly. The ribs are 18, less thick and dense than those of the manatee, the first 3 attached by cartilages to the sternum ; the shoulder blade is large, with the anterior angle rounded, the posterior extended backward with a concave margin ; the spine is prominent, and the acro- mion and coracoid processes are pointed ; the humerus is short, thick, with a prominent del- toid ridge ; the radius and ulna are very short, rounded, anchylosed at each end ; the carpal bones are 4, in two rows ; the thumb is rudi- mentary, its metacarpal bone small and point- ed; the other metacarpals are flattened, with three-jointed phalanges. The tongue is thick, the anterior upper surface with cuticular spines, and on each side at the base a horny, retro vert- ed, pointed process. The stomach is divided into two portions, the cardiac large and globu- lar, the pyloric narrower ; at the constriction between the two are two tubular csecal pro- longations as in some pachyderms, and at the cardiac end is a rounded glandular mass as in some rodents; the intestines are 14 times as long as the body, and the coscum is simple and heart-shaped. The liver is transversely ob- long, with one large and three small lobes ; the gall bladder is present, elongated, receiving bile directly from the hepatic ducts ; the spleen is very small and rounded. The heart has its ventricles deeply cleft, but not affecting the circulation;- the capacity of the pulmonary artery is very great, to accommodate the delay of the blood in the lungs during submersion. The lungs are very long, flattened, one fourth as long as the body; the superficial air cells are large, the dorsal extent is great, the trachea divides high up, and the bronchi are long, as in marine turtles ; the cartilages of the bron- chial tubes are continued spirally into each other. The sense of smell must be dull; the eye is very small and convex, with a nictita- ting membrane beside the lids; the external orifice of the ear is hardly perceptible ; the nasal openings are two parabolic slits, whose semilunar edge acts as a valve; the interior of the cheeks, according to F. Cuvier, is en- tirely covered with strong hairs. The usual length of the dugong is from 8 to 10 ft, though it has been seen as long as 20 ft. ; it is found in the seas of the East Indies, especially in the Malayan archipelago, never on land, rarely if ever in fresh water, but generally in troops where the depth is not more than three fath- oms. Its food consists of fuci and algae, and it browses on the marine vegetation as a cow does on land. It yields little or no oil, but is hunted by the Malays for its flesh, which re- sembles young beef, and is tender and palata- ble. It is generally speared, and at night, es- pecially during the northern monsoon, at the mouths of rivers, when the sea is calm. The affection of the mother for her young is very remarkable. In the Red sea is a species called H. talernaculorum by Ruppell, from his be-