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 and grooves in the plates are the remains of the original alveoli of the teeth.

The Duck-billed Platypus is, as every one knows, an aquatic animal. It is not found all over Australia, but is limited to the southern and eastern parts of that continent, and to Tasmania. The animal excavates a burrow for itself in the bank of the slow streams which it frequents. The burrow has one opening below the water and one above; and it is of some length, twenty to fifty feet. The Platypus feeds upon animal food, chiefly "grubs, worms, snails, and, most of all, mussels." These it stows away when captured into its capacious cheek-pouches. The food is then chewed and swallowed above the surface as the animal drifts slowly along. Dr. Semon, from whose work, In the Australian Bush, this account of the animal's habits is quoted, thinks that in the nature of the food of the creature the explanation of the loss of the teeth is to be found. He is of opinion that for cracking the hard shells of the mollusc Corbicula nepeanensis, upon which Ornithorhynchus mainly feeds, the horny plates are preferable to brittle teeth. Ornithorhynchus is apparently not eaten by the natives by reason of its ancient and fish-like smell. Besides, it is hard to catch on account of its diving capacities, which are aided by an acute sense of sight and of hearing. When the Duck-bill was first brought to this country it was believed to be a deliberate fraud, analogous to the mermaids produced by neatly stitching together the forepart of a monkey and the tail of a salmon.