The Porpoise resembles the dolphin in general appearance. Its length, from the tip of the snout to the end of the tail, is from five to eight feet; and the width about two feet and a half. The figure of the whole body is conical; the colour of the back is deep blue, inclining to shining black; the sides are gray, and the belly white. When the flesh is cut up, it looks very much like pork; but, although it was once considered a sumptuous article of food, and is said to have been occasionally introduced at the tables of the old English nobility, it certainly has a disagreeable flavour. Their motion in the water is a kind of circular leap; they dive deep, but soon again rise up in order to breathe. They are seen in nearly all seas, where they sport with great activity, chiefly on the approach of a squall.
The Grampus (_Orca Gladiator_) is the natural enemy of the whale and the seal, who hold him in mortal terror. His swallow is so great that he can take a porpoise or a seal whole, and has been known to swallow several in succession. The whale escapes him by getting among the ice, whither it is said the grampus will not follow him.
The Sea Cow is an aquatic vegetarian who lives on the coast. Of the three genera which constitute the family _Manatidæ_ one is now said to be extinct. The genus Manatus contains two species, one belonging to South America and the other to the West Coast of Africa. The Dugong (_Halicore Dugong_) which attains to a length of nine or ten feet at maturity produces oil having similar medicinal properties to that obtained from the Cod's liver. It inhabits the Indian Ocean, the Red Sea, the neighbourhood of the Malay Islands and the North and East coasts of Australia.
The order of hoofed animals includes a number of well known species, of which the Horse, the Ass, the Ox and the Sheep among the tame, and the Rhinoceros, the Hippopotamus, the Boar and the Bison among the wild are familiar examples. The order is divided into two sub-orders and these into numerous families. The sub-orders are, I, The Perissodactyla, which includes three families of animals characterised by an odd number of toes in their hind feet, the horse having one, and the Rhinoceros three. II, The Artiodactyla which includes seven families of animals all having an even number of toes.