228 ELBMEIiTS OF OBNITHOLOGT. 



The epiotie is superior and posterior, and shelters the posterior 

 semicircular canal. 



The two latter bones anchylose with the occipitals next to 

 them behind, before they anchylose with the " prootic." 



The earlier condition of the limb-bones of birds serves to 

 reveal their essential composition. Then we find the four 

 carpal * bones and all the three metacarpal bones distinct. 



Similarly in the leg we find the two tarsal elements distinct 

 which in adult life respectively anchylose with the distal end of 

 the tibia t and the proximal end of the tarso-metatarsal, and the 

 last-named bone plainly shows how it is made up not only of a 

 tarsal element, but of three metatarsals also. 



The wonderful egg-laying capacity of the domestic Fowl is 

 notorious both for its duration and the number laid in a nest. 

 Wild Birds of the Powl and Pheasant kind will also lay a con- 

 siderable number of eggs. Many small Birds lay and sit on 

 eight or ten eggs, and many Birds lay only five or six. Pigeons 

 lay but two, and the same is the case with Humming-birds, 

 while the Petrel and the Penguin lay but one. 



The size of the egg is not strictly related to the size of the 

 individual which lays it. Thus the Apteryx, though only about 

 as large as a moderately sized Powl, lays a very large egg. 

 The GuUlemot and the Eaven are Birds of about the same size, 

 but the egg of one is ten times the size of that of the other, 

 that of the Guillemot being as big as that of an Eagle. 



The shapes of eggs also differ considerably. Thus those of 

 the Owls are nearly round, while those of the Heron and Sand- 

 grouse are elongated with both ends nearly equal in size. 

 Everyone knows, on the other hand, that the Plover's egg is 

 pear-shaped, and some of the Guillemots lay eggs which 

 attenuate very rapidly towards the smaller end. In the Grebes 

 the eggs are pointed at both ends, although very wide in the 

 middle. 



The grain of the shell is different in different species. It is 



* Probably answering to the magnum and unciform bones of man and 

 beasts, as well as the seapho-liinar and cuneiform bones. There is also 

 sometimes a fifth carpal ossicle, whinh afterwards anchyloses with the 

 metacarpus, as also do the representatives of the magnum and wtKiforme, 

 It has been termed the pentosteon. 



t This proximal element consists at first of two distinct parts, which, as 

 they lie beneath the ends of the two leg-bones, may be distinguished as the 

 tibiale and thei fibulare respectively. 



