FISH OF ONTARIO. 19 



Series TELEOSTEI. (The Bony Fishes.) 



This group comprises the majority of existing fishes. It is apparently 

 descended from the Ganoid type. As a whole, the Teleostei differ from the 

 Ganoids in the more perfectly ossified skeleton, the less heterocercal tail, 

 the degradation of the air bladder and the arterial bulb, and in the sim- 

 plicity of the optic chiasma. 



The Teleostei are divisible into two great groups with rather ill- 

 defined boundaries, the Physostomi, or soft-rayed fishes, and the Physo- 

 clysti, or spiny-rayed. The members of the former group have through- 

 out life a slender duct, by which the air bladder is joined to the alimentary 

 canal. In most cases the fin rays are soft, the ventral fins abdominal, the 

 pectoral fins placed low, and the scales cycloid. Although the typical 

 Physostomi differ in many ways from the more specialized Physoclysti, 

 yet as we approach the junction of the two groups the subordinate differ- 

 ences disappear, leaving finally the presence of the air duct in Physostomi 

 as the only differential character. 



Subclass OSTARIOPHYSI. 



This group is characterized chiefly by the modification of the anterior 

 vertebrae. These are coossified and have some of their lateral and superior 

 elements detached and modified to form a chain of small bones, the Web- 

 erian ossicles, which connect the air bladder with the ear. 



Order NEMATOGNATHI. (Catfishes.) 



This order contains several families, which agree in having the sub- 

 opercle wanting, the anterior vertebrje coalesced, and the maxillarv 

 reduced to the bony core of a long barbel. None of the order have scales. 



Family SILURID^. (C.\tfishes.) 



Body more or less elongate, naked, or with bony plates. No true 

 scales. Anterior part of head with two or more barbels ; the base of the 

 longest pair formed by the small or rudimentary maxillary. Margin of 

 upper jaw formed by premaxillaries only. Suboperculum absent ; oper- 

 culum present. Dorsal fin usually present, short, above or in front of the 

 ventrals. Usually an adipose fin behind dorsal. First ray of dorsal and 

 pectorals usually developed as a stout spine. Lower pharyngeals separate. 

 Air bladder usually present, large and connected with the organ of hearing 

 by means of the auditory ossicles. 



A vast family of more than one hundred genera and upwards of nine 

 hundred species, mostly of the rivers and swamps of warm regions, 

 especially of South America and Africa. A few species are marine. They 

 are all very tenacious of life and most of them are excellent as food. 



