TELEOSTEI. 



407 



tractile, and is separated from the ventricle by no more than a 

 single row of valves (fig. 171, A). 



Fig. 171. A, Heart of the Angler (Lophius piscatorius). B, Arterial bulb of Bony 

 Pike (Lepidosteus) cut open. C, Heart of the same, viewed externally ; a Auricle ; 

 v Ventricle ; b Arterial bulb. 



V. The respiratory organs consist of free, pectinated, or tufted 

 branchiae, situated in two branchial chambers, each of which 

 communicates internally with the pharynx by a series of clefts, 

 and opens externally on the side of the neck by a single aper- 

 ture (or " gill-slit"), which is protected in front by a bony gill- 

 cover, and is also closed by a u branchiostegal membrane," sup- 

 ported upon " branchiostegal rays." The branchiae are attached 

 to a series of bony branchial arches, which are connected in- 

 feriorly with the hyoid bone and superiorly with the skull ; and 

 the water required in respiration is taken in at the mouth by a 

 process analogous to swallowing. 



VI. The nasal sacs never communicate posteriorly with the 

 cavity of the pharynx. 



The subdivisions of the osseous fishes are so numerous, and 

 they contain so many families, that it will be sufficient to run 

 over the more important sub-orders, and to mention the more 

 familiar examples of each. 



SUB-ORDER A. MALACOPTERI, Owen ( = Physostomata, Miil- 

 ler). This sub-order is defined by usually possessing a com- 

 plete set of fins, supported by rays, all of which are "soft" or 

 many-jointed, with the occasional exception of the first rays in 

 the dorsal and pectoral fins. A swim-bladder is always present, 

 and always communicates with the oesophagus by means of a 

 duct, which is the homologue of the windpipe. The skin is 

 rarely naked, and is mostly furnished with cycloid scales ; but 

 in some cases ganoid plates are present. 



This sub-order is one of great importance, as comprising 



