XX] MAIN DIVISIONS 493 



given rise to a good many of the groups which are now regarded 

 as primary divisions of the Teleostei. The sub-order is characterised 

 by the fact that the pelvic bones articulate with the cleithra, and 

 hence the pelvic fins are thoracic or jugular in position. The air- 

 bladder is closed, the maxilla is toothless, and there are stiff spines 

 in the dorsal, anal and pelvic fins, except in one or two primitive 

 families the pelvic fin has one spine and five soft rays. 



Only a few of the families of this enormous sub-order can be 

 mentioned. The Percidae, including the Common Perch, Perca, 

 and the Centrarchidae, including the Black River-Bass of North 

 America (Micropterus), are closely related, the first family being 

 divided from the second by having the dorsal fin divided into 

 spinous and soft fins, and by having fewer spines in the anal fin. 

 The River- or Lake-Bass is one of the fish most esteemed by anglers 

 as a sporting fish. The Serranidae closely resemble the Centrarchidae, 

 but have one of the circumorbitals produced inwards as a shelf 

 supporting the eye-ball. These are the Marine Perch, including the 

 fish called in America Sea-Bass, which are highly esteemed for the 

 table. The Mullidae or Red Mullet are distinguished by their ves- 

 tigial teeth and by having two barbels ; they are food-fish but much 

 inferior in flavour to the Mugilidae. The Sparidae include the fish 

 called the Sea-Bream, also fish of economic value distioguished from 

 Mullidae by their large teeth, which are cutting in front and crush- 

 ing at the sides. The Labridae or Wrasses are distinguished by the 

 union of the lower pharyngeal bones in the middle line and by 

 having pointed teeth like a dog's at the sides of the jaws. The 

 Wrasses include many tropical fish renowned for their brilliant 

 colours, indeed our own Wrasses assume gay colours at the breeding 

 season. The Scombridae, or Mackerel family, are distinguished by 

 having the spinous dorsal fin made up of a few feeble spines arid by 

 having the hinder part of the soft dorsal broken up into finlets. The 

 body has a characteristic shape ; it narrows behind so as to form a 

 stalk for the tail fin which is greatly enlarged and deeply forked. 

 The Mackerel, Scomber scombrus, is a most valuable food-fish. It 

 occurs in shoals chiefly off the West and East coasts and is caught 

 by seining. 



The Tunny (Thunnus thynnus) is one of the largest of food- 

 fish ; it is 10 feet in length. It is fished chiefly in the Mediterranean 

 and forms a valuable fishery. 



The HETEROSOMATA or Flat fish (often called the Pleuro- 

 nectidae) are devoid of all rigid spines in their fins and have the 



