34o SPINE-FINNED GROUP. 



present on the palatines and vomers, although absent from the tongue. The 



preopercular bone is serrated behind and at the angle, but not inferiorly; and 



the tail-fin may be either rounded, squared, or emarginate. The sea-perches of 



the genus Serranus, of which there are an enormous number of species, range 



through the seas of all the tropical and temperate regions, occasionally ascending 



tidal rivers for short distances in pursuit of prey, but being otherwise strictly 



marine. Many of the species vary considerably, both in colour and in the form 



of their tins, with age, so that specific distinctions are difficult to establish. 



Extinct species of this genus, as well as others belonging to Lates, occur in 



the middle Eocene deposits of Italy. 



The fish represented in the lower figure of the illustration on 

 Stone-Bass. r ° 



p. 339, and commonly known as the stone-bass {Polyprion cernuum), 

 is one of two species constituting a genus distinguished from the last by the 

 absence of large tusks in the jaws, and the presence of teeth on the tongue ; 

 the single dorsal fin having eleven or twelve spines, and the anal three. The 

 preopercular bone is denticulated, and there is a strongly marked rough longi- 

 tudinal ridge on the opercular. The common species is abundant on the 

 European coasts, while the second is from the seas of Juan Fernandez. Both 

 attain a very large size, ranging in weight to 80 lbs. or more, their flesh being 

 of excellent quality. The European stone -bass frequents the neighbourhood of 

 floating wood, probably for the purpose of feeding on the creatures to be met with 

 ' around such objects. 



Oriental and The two species of the genus Lates, one of which (L. niloticus) 



African Perches, inhabits the mouth of the Nile, while the second (L. calcarifer) 

 ranges from the shores of Baluchistan through the Indo-Malayan seas to China 

 and Australia, may be taken as representatives of another subfamily (Centro- 

 pomince), with three genera ; this subfamily differing from the last by the 

 extension of the lateral line on to the tail-fin, the presence of a scaly process at 

 the bases of the pelvic fins, and the small size or absence of the false gills. 

 Having no teeth on the tongue, and a divided dorsal fin, these fish may be 

 distinguished externally from the true perches by the presence of seven or eight 

 dorsal, and three anal spines. Both the preopercular and preorbital bones are 

 serrated, and the latter denticulated at the angle ; the finely pectinated scales 

 being of moderate size. The Indian perch, which may grow to a length of 5 feet, 

 is the only Oriental member of the family which commonly ascends rivers to any 

 distance. When taken in the larger rivers its flesh is excellent for the table, 

 great quantities being sold in the Calcutta market, where it is commonly known 

 by the name of cock-up. The allied genus Psammoperca is represented by two 

 species, one ranging from Australia to China, while the other is exclusively 

 Australian. There are many other generic representatives of this extensive 

 family, which are far too numerous to mention, no less than twenty-seven 

 occurring within the limits of British India, Among these the Indian genus 

 Pristipoma, which is referred by some writers to a separate family, is represented 

 by extinct species in the middle Eocene of Italy ; and it may be mentioned here 

 that the earliest known forms of the family are the extinct genera Podocys and 

 Acanus from the lower Eocene of Switzerland. 



