248 MAMMALIA OF INDIA. 
The fin on the back is horizontal, and not rayed and upright like that of 
a fish; the tail resembles that of a fish in form, the caudal vertebree 
running through the middle of it. The immense muscular power of this 
tail, with its broad flanges, arises from the flesh of the body, terminating 
in long cords of tendon, running to the tip. The vertebral column is 
often ankylosed in the fore-part, but is extremely elastic, owing to the 
cartilaginous cushion between each bone in the latter half. Thus, 
whilst the fore-part is rigid, the hinder is flexible in the extreme. The 
brain is large and much convoluted; the heart is very large, and the 
blood-vessels extremely full and numerous, with extensive ramifications, 
which, being filled with oxygenated blood, assist in supporting life whilst 
submerged. ‘The lungs are also very large. The laryngeal and nasal 
passages are peculiar. The following description is by Dr. Murie: “ In 
front of the larynx of man we all know that there is an elastic lid, the 
epiglottis, which folds over and protects the air passage as food is 
swallowed. The side cartilages constitute the walls of the organ of voice 
and protect the vocal chords. Now, in the comparatively voiceless 
wh: le, the cartilages, including the epiglottis, form-a long rigid cylindrical 
tube, which is thrust up the passage at the back of the palate in con- 
tinuity with the blew-hole. It is there held in place by a muscular ring. 
With the larynx thus retained bolt upright, and the blow-hole being 
meanwhile compressed or closed, the cetacean is enabled to swallow 
food under water without the latter entering the lungs.” The stomach 
is peculiar, being composed of several sacs or chambers with narrow 
passages between ; the intestines are long, glandular and, according to 
Dr. Murie, full of little pouches. There is no gall bladder ; the gullet is 
very narrow in some and wider in others. Some have teeth, others are 
without. The eyes are small ; the ears deficient externally, though the 
interior small ear-bones of ordinary mammals are in these massive and 
exceedingly dense, so much so, as Murie observes, as to be frequently 
preserved fossil when other osseous structures are destroyed. 
The cetacea have been divided into the Denticete, or Toothed Whales, 
and the JZysticete, or Whalebone Whales. The former contains the 
river dolphins, the ziphoid whales, the gigantic sperm whale, the 
sea dolphins, and the narwhal or sea unicorn. The latter contains the 
baleen whales, 
DENTICETE—THE TOOTHED WHALES. 
None of the larger species are found on these coasts, or in the Indian 
Ocean, the two most interesting of which are the gigantic sperm whales 
(Physeter macrocephalus), and the curious narwhal or sea unicorn 
(Monodon monoceros). ‘The latter is an inhabitant of the northern seas 
only, but the sperm abounds in warmer waters, being frequently found 
