ORDERS OF FISHES. 241 



Order III. Teleostei. 



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

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

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

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

 vertebral column always consists of more or less completely ossified 

 vertebrse ; and the two pairs of limbs, 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 bulbils 

 arteriosus is not capable of regular contractions, and is separated 

 from the ventricle by only a single pair of valves. 



Fig. 173. — The common Perch (Perm JluviatUis). o Gill-cover, ^vith the gill-slit behind 

 it ; p One of the pectoral flns, the left ; v The left ventral fln ; d The first dorsal 

 fin ; d' The second dorsal fin ; c The caudal fin or tail ; a The anal fln ; I Lateral 

 line. 



The order Teleostei comprises almost all the most familiar fishes, 

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

 were taken 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 more 

 or less completely ossified, and does not remain cartilaginous through- 

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

 consists of a number of distinct vertebra. The vertebrae, however, 

 are " amphicoelous," 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 remains 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 



