REPTILIA. 167 



wider at the end than towards the head ; the nostrils nearer to its back and 

 base. Their legs being shorter than those of geese, and placed farther back, 

 renders walking more difficult to them than to the latter. 



The species of the first division, or those whose thumb is bordered with a 

 membrane, have a larger head, a shorter neck, the feet placed farther back, 

 smaller wings, a stiffer tail, more compressed tarsi, longer toes, and the mem- 

 brane of the feet more entire. They walk with more difficulty, feed more ex- 

 clusively on fish and insects, and dive more frequently. 



Ducks are now distributed into various subgenera : such as Oidemia (the 

 Scoter, Velvet Duck, Black Duck) ; Clangula (Long- tailed Duck) ; So mater ia 

 ( Eider Duck) ; Fuligula (Red-head, Pochard Duck, Tufted Duck) ; Rhyn- 

 chaspis (The Shoveller); and Tadorna (The Sheldrake, Muscovy Duck), 

 originally from South America, where it perches on trees, and the An. boschas, 

 Lin. (or Mallard), the stock of our common tame Duck, Teal, &c. 



MERGUS, Linnceus. 



The genus of the Mergansers comprehends those species in which the bill, 

 thinner and more cylindrical than that of the ducks, is 

 armed along its edges with small pointed teeth resembling 

 those of a saw, and directed backwards ; the tip of the 

 upper mandible is hooked. Their carriage and even 

 plumage are those of ducks, properly so called ; but their gizzard is less mus- 

 cular. The inflation of the lower larynx in the males is enormous, and partly 

 membranous. They live on lakes and ponds, where they are very destructive 

 to fish. 



Merg. Merganser, Lin. (The Goosander.) Is the size of a duck, and has 

 red feet and a bill of the same hue. The head of the old male is of a deep 

 green, the feathers on its summit forming a sort of toupee; the mantle is black, 

 with a white spot over the wing ; underneath and the neck slightly tinged 

 with rose-colour. 



CLASS III. 



REPTILIA. 



THE disposition of the heart in Reptiles is such, that at each con- 

 traction, a portion only of the blood it has received from the different 

 parts of the body is transmitted to the lungs, the remainder returning 

 to those parts without having passed through the pulmonary organs, 

 and without having respired. 



The result of this is, that the action of oxygen upon the blood is 

 less than in the Mammalia, and that if the quantity of respiration in 

 the latter, in which all the blood is compelled to pass through the 



