488 ZOOLOGY, 
Order 2. Proteida.—Body flattened, with persistent gills, and gilt 
openings; a maxillary bone. (Proteus, Necturus.) 
Order 8. Urodela.—No persistent gills, body with a tail ; no gill-open- 
ings except in Menopoma and Amphiuma, (Salamandra.) 
Order 4, Gymnophiona.—Body snake-like, no feet; no tail ; young with 
gills. (Cocilia.) 
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 ; larve 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. 
Crass VII.—Reptizia (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 ina 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 calied Sawropsida. 
Thus no one class of Vertebrates stands alone by itself ; every 
year fresh researches by paleontologists, 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 
