ORDERS OF FISHES. 



241 



Order III. Teleostei. 



The fishes comprised in this onler, as implied in their name, have 

 a well-ossified or bony skeleton, and they are commonly known as 

 the "Bony Fishes." In all the Tdeostn, the skeleton is bony, the 

 skull is composed of distinct bones, and there is a lower jaw. The 

 vertebral column alwa3's consists of more or less com])letely ossified 

 vertebra; ; and the two pairs of limVis, when present, are in the form 

 of fins, supported by rays. The gills are free, comb-like or tufted 

 in shape, and always protected by a bony gill-cover. The hiilhtm 

 arteriosus is not capable of regular contractions, and is separated 

 from the ventricle by only a single paii- of valves. 



Fig. 173. — The common Perch (Perca Jluviatil is), o Gill-cnver, with the gill-slit beiiiinl 

 it ; p One of tlie pectoral fins, tlie left; v Tlie left vciiti'al fin : (( The first dorsal 

 Tin; ((' Tlie second clursal lin ; c Tlie caudnl lin .ir tuil : c The anal fin; (Lateral 

 lini:. 



The order Teleostei comprises almost all the most familiar fishes, 

 and it will be unnecessary to dilate here upon their structure, as tliey 

 were takeu as the type of the class in describing the fishes generally. 

 It may be as well, however, to recapitulate some of the leading points 

 in the anatomy of the Bony Fishes. 1. The skeleton is always moi-e 

 or less completely ossified, and does not remain cai-tilaginous through- 

 out life. The notochord is not permanent, and the vertebral column 

 consists of a number of distinct vertebrte. The vertebri-e, however, 

 are " amjjhicoelous," or hollow at both ends, so that there is left 

 between each pair a doubly conical cavity, which is filled with the 

 cartilaginous or semi-gelatinous I'emains of the notochord. In this 

 way an extraordinary amount of flexibility is given to the entire 

 vertebral column. In no fish (except the Bony Pike, which belongs 



