394 NOTES. 



vertebrae vary in form : in the lowest they are biconcave, like those of Fishes ; 

 in Salamanders they are opisthoccelous : in the Frogs and Toads they are 

 usually procoelous. 



'** Salamanders are often taken for Lizards, but differ in having gills in 

 early life and a naked skiu. The Proteus and Siren resemble a tadpole ar- 

 rested in its development. 



"^ The Surinam Toad has no tongue. 



^^ The posterior pair of limbs is sometimes represented by a pair of small 

 bones ; and the Boas and Pythons show traces of external hind-limbs. 



"5 There are some notable exceptions. The Slow-worm is legless, and 

 the Chameleon has a soft skin, with minute scales. 



'^' According to Owen ; but Huxley insists that the plastron belongs to the 

 exoskeleton. 



"' Knees always bend forward, and heels always bend backward. 



168 We cannot claim that this airy skeleton is necessary for flight. The 

 bones of the Bat are free from air, yet it is able to keep longer on the wing 

 than the Sparrow. The common Fowl has a hollow humerus ; while some 

 Birds of long flight, as the Snipe and Curlew, have airless bones. 



"'The fossil Archceopttryx, a lizard- like Bird, is placed in a separate 

 division, Saururoe. Birds have also been divided according to their degree 

 of development at birth into (1) Hesthogenmis, as Fowls, Ostriches, Plovers, 

 Snipes, Rails, Divers, and Ducks, whose chick is hatched completely clothed, 

 has perfect senses, runs about, and feeds itself. When full grown, it uses its 

 first opportunity to settle on land or water, not on trees; the male is po- 

 lygamous and pugnacious ; the female makes little or no nest ; and neither 

 sex sings. Tliis group is of the best use to man, and approaches more nearly 

 to Mammals, the habitual use of the legs and preference for land or water 

 degrading it as a Bird and raising it in the list of animals ; (2) Oymnogenam, 

 as Gulls, Pelicans, Birds of Prey, Herons, Sparrows, Woodpeckers, and 

 Pigeons, whose chick comes helpless, blind, and naked ; it can neither walk 

 nor feed itself, but gapes for food ; the adult is monogamous, and builds 

 elaborate nests in trees and perche.s; many sing; all are habitual flyers. 

 These are birds juar excellence, gifted with higlier intelligence than the others, 

 and are never domesticated for food. 



"" Hopping is characteristic of and confined to the Perchers ; but many of 

 them, as the Meadow-lark, Blackbird, and Crow, walk. 



'" This order is artificial. But it is better to retain it until ornithologists 

 agree upon some natural arrangement. The classification of birds is taken 

 from Coues's " Key to North American Birds,"-as being the work on orni- 

 thology in most general use. 



"' The whales are hairy during foetal life only. 



"' The Manatee has 6; HoiTmann's Sloth 6; and two species of three-toed 

 Sloth have respectively 8 and 9. 



"■• As in the Whale, Porpoise, Seal, and Mole. Teeth are wanting in the 

 Whalebone Whales, Ant-eaters, Manis, and Echidna". 



'" The Monotremes resemble Marsupials in having marsupial bones, but 

 have no pouch. They differ from all other Mammals in having no distinct 

 nipples. 



