a0 Elementary Manual of Zoology. 
mango-fish, which ascends the Ganges and other rivers in the hot 
weather. Scienid@, such as the whiting of the Bay of Bengal, 
which is excellent eating when freshly cooked, but rapidly 
becomes insipid after death. Ladyrinthiet, such as Anibas scandens, 
which is almost amphibious. 
(c) Dipnoi.—These fish are not found in India, so are of no practical 
importance, but itis useful to notice them, as they have the 
swimming bladder converted into lung-like organs, which enable 
them to breathe air as well as water. They are thus interme- 
diate between fish and amphibia. They occur in Australia, 
Africa, and South America. 
AMPHIBIA, 
These are cold-blooded Vertebrata, usually with a naked skin. 
They breathe as larve by gill slits, and as adults by lungs. For details 
of the structure of a typical Amphibian reference should be made to the 
chapter on the dissection of the Frog. The chief Amphibia to be met 
with in Indiaare the bull-frogs, little brown frogs, tree-frogs, and toads. 
Tu their adult condition these animals feed on insects and probably 
destroy a good many destructive species, but they are of no very great 
economic importance. The chief point to remember about the Amphibia 
is that they connect the fish with the reptiles and birds on one side and 
with the mammals on the other. 
REPTILES. 
The reptiles comprise a number of cold-blooded air-breathing 
vertebrates, of which the most important are the Chelonia (turtles 
and tortoises), the Lacertilia (lizards), the Ophidia (snakes), and the 
Crocodilia (crocodiles), Reptiles resemble birds in having the mandible 
articulated to the skull by a pair of quadrate bones, and in having the 
skull articulated to the vertebral column by a single occipital condyle. 
Students should verify these points by comparing the skull of a reptile 
with that of a bird. They should also notice the difference in each 
case from the skull of a mammal where there is no quadrate bone 
visible but two occipital condyles. Reptiles are cold-blooded ; they 
are covered with scales ; the heart consists of two auricles and a ven- 
tricle, the latter being more or less completely divided into aright and 
left chamber. Two aortic arches are present, but the right arch is in 
many cases the larger and more developed, thus indicating an advance 
in the direction of the arrangement found in birds, where the right 
aortic arch alone persists. 
(2) Chelonia (Turtles and Tortoises).—Body compressed, covered 
with a bony dermal skeleton, the dorsal portion uniting 
