THE PERCH TRIBE 2703 



the intestine without a spiral valve, and the skeleton fully ossified. From the 

 Physostomi, the Physoclystous group are distinguished by the general absence of a 

 duct to the air bladder (when present), by the parietal bones of the roof of the 

 skull being always separated from one another by the intervention of the supraoc- 

 cipital, and by the pelvic fins being in most cases either thoracic or jugular* in 

 position. Regarding, however, the spine-finned fishes as constituting a separate 

 suborder, they are distinguished, in addition to the foregoing characteristics, by 

 some of the anterior rays of the dorsal, anal, and pelvic fins usually taking the 

 form of strong, unjointed, bony spines. It must, however, be acknowledged that 

 this characteristic is one of but little importance; some of the hairtails ( Trichiurida} 

 scarcely possessing what can be denominated true spines, while these are also want- 

 ing in the family (Scombresocida} to which the flying fishes belong. In all cases the 

 gills are comb-like, the pectoral arch is suspended from the skull, and interclavicles 

 are wanting. 



THE PERCH TRIBE Family PERCID^ 



The first representatives of the spine-finned fishes are the perches, which, with 

 several allied families, belong to a sectional group {Pertiformes) of the suborder, 

 characterized by the lower pharyngeal bones being generally separate, and the 

 scales usually of the ctenoid type. The preopercular bone of the gill cover has na 

 bony stay connecting it with the eye; the spinous portion of the dorsal fin is well 

 developed; none of the additional rib-like bones known as epipleura are attached to 

 the bodies of the vertebrae; the pelvic fins are thoracic in position, and have usually 

 five (rarely four) branched rays; and the supporting bones (pterygials) of the 

 pectoral fins are longer than broad, and of a more or less distinctly hourglass form. 

 The Perch family, as restricted by Mr. Boulenger, is distinguished by the following 

 characteristics: In the skeleton the anterior vertebrae have no transverse proc- 

 esses, but in the dorsal part of the series all or most of the ribs are attached to 

 such processes. There are two nostrils on each side; the gill membranes are free 

 from the isthmus or space between the two branches of the lower jaw and gill 

 openings; there are four pairs of gills, with a slit behind the fourth; the gill rays 

 or branchiostegals vary from six to eight on each side; more or less fully-developed 

 false gills are generally present; the soft portion of the dorsal fin is not very much 

 more developed than the anal, and the latter has either one or two spines. In 

 common with the two following families, the perches are further characterized by 

 the general presence of a lateral line, continuous from the head to the tail, the usual 

 absence of scales from the median fins, the simple conical teeth, and the absence of 

 barbels round the mouth. In form the body is more or less elongate, compressed, 

 and cylindrical; although rarely it may be slightly compressed. As now restricted , 

 the family includes a dozen genera inhabiting the fresh waters of North America, 

 Europe, and Western Asia; but the members of the genera Lucioperca and Percarina, 

 enter salt water. All are carnivorous. 



* They are said to be thoracic when in the same vertical line as the pectoral fins, and jugular when in 

 advance of them. 



