488 ZOOLOOY. 



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

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



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

 inga except in Menopoma and Ampbiuma. (Salamandra.) 



Order A. GtyrmuypMonn. — Body snake-like, no feet; no tail ; young with 

 gills. (Coecilia.) 



Order 5. Stegocepliala. — 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, Eana.) 



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 tbe 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 VI. — Reptilia (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 {Icthyop- 

 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 



