MONOTREMES. PLATE XV. 
Egg-laying Mammals: 1. Skeleton of Ornithorhynchus anatinus. 2, Skele- 
ton of Echidna hystrix. 3. Egg of Ornithorhynchus, showing the shape, 
after St. Hilaire. 4. Young Ornithorhynchus. 5. Head of young Or- 
nithorhynchus, 6. Mammary gland, pouch, and young of Echidna hys- 
trix. 7. Apertures of mammary gland of Ornithorhynchus anatinus. 
