488 ZOOLOGY. 



Order 2. Proteida. Body flattened, with persistent gills, and gill- 

 openings ; a maxillary bone. (Proteus, Necturus.) 



Order 3. Urodela. No persistent gills, body with a tail ; no gill-open- 

 ings except in Menopoma and Amphiuma. (Salamandra.) 



Order 4. GymnopMona. Body snake-like, no feet ; no tail ; young with 

 gill-opeuings, but no gills. (Coecilia.) 



Order 5. Stegocephala. Extinct forms ; the temples with a bony roof; 

 often large ; either snake-like, without limbs, or with pad- 

 dle-like limbs, or with four legs ; teeth with or without 

 labyrinthine structure. (Archegosaurus, Labyrinthodon.) 



Order 6. Anura. Body short, tailless, with four limbs ; toes very long ; 

 leapers ; larvae tailed. (Bufo, Rana.) 



Laboratory Work. The student should carefully follow, with a speci- 

 men in hand, the description of the structure of the frog, aided by the 

 figure ; then should make a skeleton of the same species. These 

 studies should then be followed by a close comparison with the struc- 

 ture of a mud-puppy and of a salamander the osteology and anat- 

 omy of the softer parts receiving equal attention. The breeding hab- 

 its of the Batrachians may be studied by confining them in jars or 

 aquaria. The embryology can best be studied by hardened stained 

 sections of the eggs. 



CLASS V. EEPTILIA (Lizards. Snakes, Turtles, and 

 Crocodiles). 



General Characters of Reptiles. In the members of the 

 present class we have a still farther elaboration of a type of 

 structure which first appears in the Batrachians, with the 

 addition of features, which on the other hand are wrought 

 out in a more detailed manner in the birds, so much so that 

 while the fishes and Batrachians form one series (Ictliyop- 

 sida), a study of different fossil reptiles, especially the bird- 

 like reptiles (Dinosaurs and Pterosaurs), which clearly con- 

 nect the birds with the reptiles, shows that the two latter 

 groups should be united into a series called Sauropsida. 

 Thus no one class of Vertebrates stands alone by itself ; every 

 year fresh researches by palaeontologists, and the re-examina- 

 tions of living Vertebrates, especially as to their embryonic 

 history, proves that no single class, not even a type so well 



