466 Vertebrata., 



pecker (P. viridis) ; and the Spotted "Woodpeckers, the Large {P. 

 major), the Medium (P. me(Jms),and the Small (P. minor). The Three-toed 

 Woodpecker (P. tridactylus), .in which the inner hind toe (hallux) is lost, 

 occurs in the Alps. The Wryneck {lynx torquilla), is a near ally ; beak 

 conical, not keel-Uke ; the tail feathers are not stifE enough to act as a support ;, 

 migratory, visiting England in the spring. 



3. Parrots {Psittacidss) have an uncommonly short, thick, much arched 

 beak, overhanging a short mandible ; the beak is freely movable ; the tongue, 

 thick and soft. They are brightly-coloured (green, red, etc.) and plant-eating ; 

 they are found in the Tropics. They may be divided into several groups : (1) 

 Cockatoos {Plictolophinse), of Asia and Australia, with an upright tuft of 

 feathers on the head, often brightly-coloured plumage ; (2) P a r r a k e e t & 

 (Sitiacinx), with long tails; (3) True Parrots [Psittacinse), with short tails, 

 and without the crest of feathers on the head; (4) Lories (Trichoglossinx), of 

 Australia, the tip of the tongue is brush-like in consequence of numerous long, 

 filiform, homy papillae ; (5) Stringopinx, owl-like Parrots, of which there is only a 

 single genus in New Zealand {Stringops habroptilus). The last are nocturnal, 

 with soft, dark greenish plumage, living by day in holes in the ground, where 

 also they nest ; they fly very little, or not at all (the sternal keel is reduced) 

 and for the most part move about on the ground. 



4. Toucans {Eham.phastidx) have a very large, thick, somewhat curved 

 beak, which is often notched at its edges, and which is almost as long as the 

 whole body ; the tongue is narrow, homy, and frayed out at its margin. They 

 are South American forms, of medium size, and with gorgeous colouring. 



Class 6. Mammalia. 



As regards external configuration, tlie Mammalia are usually 

 characterised by the possession of a very pronounced neck, varying 

 considerably in length ; of a much reduced tail, with no locomotor 

 significance, and of little use ; of limbs, so well-developed, on the- 

 other hand, that the body is raised some distance off the ground : the 

 elbows are turned backwards; the knees, fingers, and toes forwards- 

 In many cases the animal does not rest upon the whole foot, but only 

 on the toes, or even their tips, whilst the rest is raised, and contributes, 

 to the lengthening of the limb.* Within the class, besides the- 

 ordinary walking type, various others are specialised, such as. 

 springing, fiying, swimming forms (c/., Reptilia). When the body is 

 adapted to a peculiar mode of life, the outer form may be very 

 aberrant. This is especially noticeable in certain aquatic Mammalia 

 (Whales), where the neck is reduced to a minimum j the limbs are 

 very degenerate, whilst the tail attains enormous proportions, so that 

 the appearance is in the highest degree piscine. 



The skin consists of the usual layers (dermis, and epidermis with 

 stratum corneum and stratum mucosum or Malpighii) ; on the surface 

 of the dermis there are p a p i 1 1 £e extending into the Malpighian 

 layer. Pigment may be present in the epidermis (in both layers), and 



* The limbs are longest, and the sxirfaces touching the ground smallest in the. 

 swiftest animals (tTngulata) 



