Systematic Course. 57 
development the Amphiowus is of the very greatest in- 
terest, as it helps us to understand how the Vertebrata. 
came to be what they are; but the subject is one which 
is too complicated to enter upon in this elementary work. 
(ce) Cyclostomi,—This group comprises the hags and lampreys, 
some of which are of considerable size. They are mostly 
more or less marine, some of the species being parasitic. 
They are of no practical importance to the Indian 
forester, but should be noticed, as they comprise a very 
well-marked section of the Chordata. They may be de- 
fined as eel-like Chordata, with persistent notochord and 
skull, but without lower jaw or paired fins, 
(2) Vertebrata,—This group comprises all the fish, amphibia, 
reptiles, birds’ and mammals, and is hence of the utmost 
importance. The chief points in which the Vertebrata 
differ from the other groups of Chordata are in possessing 
a lower jaw and paired limbs, and in the modification of 
the notochord into a vertebral column. The various sec- 
tions of, the group will be considered under the headings 
of Fish, Amphibia, Reptiles, Birds and Mammals. 
Fisa. 
Fish are cold-blooded aquatic Vertebrates, with paired pectoral and 
pelvic fins (corresponding to the fore and hind limbs of the higher 
Vertebrata). They breathe by gills throughout life. For an account 
of the anatomy of a typical fish, see the chapter on the dissection of the 
Mahseer. 
Omitting the Ganoids, which are of no immediate importance, the 
chief groups of fishes are the Chondropterygii (cartilaginous fishes), the 
Teleostei (bony fishes), and the Dipnoi (amphibious fishes). 
(2) Chondropterygii.—These fish breathe exclusively by gills 
and have the muscles supported by a cartilaginous skeleton. 
They comprise the sharks, dogfish, sawfish and skates 
and rays, which are very abundant round the coasts of 
India. They are largely carnivorous, some species being 
dangerous to human life. They are also of some slight 
importance economically, as the livers of many of the 
sharks are used for making oil, the skins are made into the 
shagreen employed for covering knife handles and sword 
scabbards, while glue is made out of the fins of many 
species, and the flesh of most of the species is used for 
food. : 
(2) Teleosteii—These fish breathe exclusively by gills, and have 
the muscles supported by a bony skeleton, They comprise 
