308 Dr. H. Woodward — On Wingless Birds. 



VI. — On " Wingless Birds," Fossil and Eecent ; and a Few 

 Words on Birds as a Class, 



By Henry Woodward, LL.D., F.R.S., F.G.S. 

 (Eead before the Geologists' Association, May 1st, 1885.) 



BEFORE offering a short account of the Struthious, or Ostrich- 

 like Birds, commonly called " Wingless Birds," I propose to 

 say a few words about Birds as a class. 



Every one who has paid attention to the anatomy of Bii'ds has 

 been struck by the marvellous uniformity of the Class. Embracing 

 as it does almost countless numbers of species, these are found upon 

 examination to pass insensibly, by the most delicate differences, the 

 one into the other, so that it often is most difficult to distinguish 

 genera and species. 



"Though this class," says Prof. Huxley, "contains a great num- 

 ber of specific forms, the structual modifications which they present 

 are of comparatively little importance : any two birds which can be 

 selected diffei'ing from one another less than the extreme types of 

 Lacertilia, and hardly more than the extreme types of Chelonia 

 do." 



If we take up a bird's skull, we shall find that the vertebral column 

 articulates to the head by a single occipital condyle. That each 

 ramus of the lower jaw is composed of a number of pieces which 

 are distinct in the embryo : the jaw itself being united to the skull, 

 not directly, but by the intervention of the "quadrate bone," as in 

 reptiles. 



That the fore-limb (manus) in no existing bird possesses more 

 than three fingers, or digits, and the metacarpal bones are anchy- 

 losed together. Also we notice that the fore-limb in all living birds 

 is useless as an organ of prehension, and that in most it serves as an 

 organ of flight. 



That the hind-limb in all birds has the ankle-joint between the 

 bones of the tarsus ; the astragalus and calcaneum uniting with the 

 distal end of the tibia and the lower bones with the metatarsus, 

 which in birds is called the " tarso-metatarsal " bone. 



[The heart has 2 auricles and 2 ventricles, the right and left sides 

 being completely separated from each other; nor is there any com- 

 munication between the pulmonary and systemic circulation as there 

 is in reptiles. 



The respiratoi'y organs are in the form of spongy cellular lungs, 

 not freely suspended in pleural sacs, and the bronchi open on the 

 surface with a number of air-sacs, placed in different parts of the 

 body.] 



All birds are oviparous, none bringing forth their young alive, or 

 being ovoviviparous, as is the case with some of the reptilia. 



All birds are provided with an epidermic covering specially 

 modified so as to constitute what is known as " feathers." 



Lightness and strength characterize the bones of the bird's 

 skeleton. The walls of the bones, although very thin, contain a 

 large amount of phosphate of lime, which gives them great compact- 

 ness. 



