CHAP. V DR. SEMON'S observations I I 5 



grooves in tlie plates are the remains of the original alveoli of 

 the teeth. 



The Duck-billed Tlatypus 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, chietly " 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 ex- 

 planation of the loss of the teeth is to be found. He is of 

 opinion that for cracking the hard shells of the mollusc Corhicnla 

 nepeanensis, upon which Ornithorhyyichus mainly feeds, the horny 

 plates are preferable to brittle teeth. OrnWiorhynchus is appar- 

 ently not eaten l)y 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 fore- 

 part of a monkey and the tail of a salmon. 



