TORTOISES. S 



and it is in an especial manner in their production that Nature seems to 

 have amused herself by imagining the most fantastic shapes, and by mo- 

 difying in every possible way the general plan she has followed in the 

 construction of the Vertebrated animals, and in the Oviparous classes 

 especially. 



The comparison, however, of their quantity of respiration and of their 

 organs of motion, has enabled M. Brogniart to divide them into four 

 orders*, viz. 



The Chelonia, or Tortoises, whose heart has two auricles, and whose 

 body, supported by four feet, is enveloped by two plates or bucklers form- 

 ed by t1ie ribs and sternum. 



The Sauria, or Lizards, whose heart has two auricles, and whose 

 body, supported by four or two feet, is covered with scales. 



The Ophidia, or Serpents, whose heart has two auricles, and whose 

 body always remains deprived of feet. 



The Batrachia, whose heart has but one auricle, and whose body is 

 naked; most of these pass, with age, from the form of a fish breathing by 

 branchiae, to that of a quadruped breathing by lungs. Some of them, 

 however, always retain their branchi^, and a few have never more than 

 two feetf. 



ORDER I. 



CHELONIA.— THE TORTOISES. 



The Chelonia, better known by the name of Tortoises, have a heart cora- 

 posed of two auricles, and of a ventricle divided in two unequal cavities, 

 which communicate with each other. The blood from the body is poured 

 into the right auricle, that from the lungs into the left, but the two streams 

 become more or less mingled in passing through the ventricle. 



These animals are distinguished at the first glance by the double shield 

 in which the body is enveloped, and which allows no part to project ex- 

 cept their head, neck, tail, and four feet. The upper shield, called cara- 



• Al. Brogniart, Essai d'une Classification Naturelle des Reptiles, Paris, 1805, and 

 in the Mem. des Sawints Efrang., torn. 1, p. 587. 



t The Sauria and Ophidia are differently arranged by some others, Merrem, for 

 instance. They detach the crocodiles, to form a separate order, and unite the first 

 family of the Ophidia or Anguis to the remainder of the Sauria, a distribution which 

 is founded on some peculiarities in the organization of crocodiles, and on a certain 

 resemblance of Anguis to the Lizards. We merely indicate these affinities, which 

 are almost wholly internal, preferring a division more easily applied. 

 b2 



