l'.".U AYES. 



ripally inhabit sluggish rivers and ponds. Cixtudx r // rojifra Schneid. = 

 (ir-n.. the common Tortoise of South Europe and East Germany ; Ennjs 

 dii the Caspian Sea. in Dalmatia and Greece ; Clniijilru serpent iua L.. with very 

 sliarp jaws, in North America. 



Fam. Chersidse. Land Tortoises. With high, arched, ossified carapace; 

 head and feet retractile. The digits are immovably connected as far as the 

 nails to thick club-feet, with indurated soles. They live in damp and shady 

 localities in warm and hot climates, and feed on plants. Trxturfo grcrca L. r 

 Alclr.. = nninjinata. South Italy : T. tnlniluta Baud., in America. 



CHAPTER VIII. 

 Class IV. AVES* BIRDS. 



Warm-blooded oviparous animals, covered with feathers. The cham- 

 bers of the heart are completely separated. The rlyht aortic arcJi 

 persists. There is a single occipital condole, and the anterior limbs are 

 transformed into winys. 



As opposed to the poikilothermic Vertebrates (i.e., Vertebrates 

 whose temperature varies with that of the external medium) the 

 blood of Ares and Mammalia possesses a high temperature, which 

 remains tolerably constant in .spite of the changing temperature of 

 the external medium. This maintenance of a constant temperature 

 demands above everything a great energy of metabolism. The sur- 

 face of all the vegetative organs, especially of the lungs, kidneys, and 

 alimentary canal, has a relatively greater extension in the warm- 

 Wooded than in the cold-blooded animals. The operations of diges- 

 tion, preparation of blood, circulation and respiration are carried on 

 with much greater energy. With the need of a richer nourishment, 

 the processes of vegetative life take a disproportionately more rapid 

 course, and as the high and uniform temperature of the blood is a 



Joh. F. Naumann, ' Xaturgeschichte der Vogel Deutschlands," 13 Bde.,, 

 Stuttgart. 1822-lsr.n. 



" Naumanuia. Archiv t'iir Oruithologie," Herausgegeben von Ed. Baldamus. 

 Kothen, 1841). 



" Journal fiir Ornithologies' Herausgegeben von J. Cabanis. Cassel. 1853 . 



"The Ibis," 1859. 



Tiedernann. " Anatomie und Naturgeschichte der Vogel." Heidelberg. 1810- 

 1814. 



C. E. v. Baer. " Entwickelungsgeschichte der Thiere.'' I. und II., 1828-1837. 



Rernak. " Untersuch. iiber die Entwick. der Wirbelthieiv." I'.crlin. 1850-5."). 



Huxley, " On the Classification of Birds." Proceed. Zool. Soc.. 



Gray and Mitchell. "The Genera of Birds," London, 1841-1'.). 



C. Sundevall. ' Tentamen." Stockholm, 1872-73. 



