OVIPARA. 215 



OF THE OVIPAROUS VERTEBRATA. 



Although the three classes of the Oviparous Vertebrata 

 differ greatly from each other in their quantum of respiration, 

 and in all that relates to it, viz. the power of motion and the 

 energy of the senses, they present several common characters 

 w^hen opposed to the Mammalia, or Viviparous Vertebrata. 



The hemispheres of their brain are very slender, and are 

 not united by a corpus callosum ; the crura of the cerebellum 

 do not form that protuberance called the pons Varolii; the 

 nates at least in two of these classes become greatly de- 

 veloped, contain a ventricle, and are not covered by the hemi- 

 spheres, but are visible below, or on the sides of the cere- 

 brum ; their nostrils are less complex ; the ear has not so 

 many small bones, which in several are totally wanting; the 

 cochlea, when it exists, which is only the case in Birds, is 

 much more simple, &c. Their lower jaw, always composed 

 of numerous pieces, is attached by a concave facet to a salient 

 process, which belongs to the temporal bone, but separated 

 from its petrous portion ; the bones of their cranium are more 

 subdivided, although they occupy the same relative places, 

 and fulfil similar functions; thus the os frontis is composed 

 of five or six pieces, &c. The orbits are merely separated 

 by an osseous lamina of the sphenoidal bone, or by a membrane. 

 When these animals have anterior extremities, besides the 

 clavicle, which is frequently united. to its fellow on tlie oppo- 

 site side, and is then called fourchette, the scapula also rests 

 upon the sternum, by a very broad and long coracoid apophy- 

 sis. The larynx is more simple, and has no epiglottis; the 

 lungs are not separated from the abdomen by a perfect dia- 

 phragm, &c. To render all these affinities sensible, however, 

 it would be necessary to enter into anatomical details, which 



