The Spine-finned Teleostei 379 



Islands, Seychelles, Indian Ocean, Malay Archipelago, New 

 Guinea and Caroline Islands. (255:36-40). 



The small family of the Nandidae shows close affinity 

 with the Centrarchidae, through such genera as Lepomis 

 and specially Kuhlia. Like the latter genus also the distri- 

 bution is striking. For Badis, Catopra, and Nandina are 

 found in freshwaters from Bengal to Borneo and thence 

 to the Moluccas, Polycentropsis occurs in West Africa, 

 while the highly modified Polycentrus and Monocirrus occur 

 in freshwaters of Essequibo and Brazil. But these again 

 lead almost insensibly, as Giinther and others have sug- 

 gested, to the group of families that in the older classifica- 

 tions were known as the Pharyngognathi. 



The Percidae are even more suggestive. While 7 of 

 the 12 recognized genera are purely N. American, and one 

 rather primitive genus Etheostoma alone includes 45 

 species, the two relatively recent and highly evolved genera 

 Perca and Lucioperca include between them 8 species, some 

 of which are N. American, and others are common to W. 

 and E. Europe on to West and East Central Asia. These 

 therefore, probably crossed the N. Atlantis and Islandic 

 bridge, and later spread into E. Asia during Miocene time. 

 Such would explain also the presence of three highly evolved 

 genera, namely of Aspro in the Danube, of Amper in the 

 Rhone, of Percarina in the Black and Azov Sea areas, and 

 of Acerina from Britain eastward through central and 

 north Europe to the Danube, Galicia, S. Russia, and thence 

 eastward to Lake Baikal (Fig: GG) . 



The family that has not inappropriately been called 

 popularly the Sea Perches, namely the Serranidae, now de- 

 serves consideration. For the included genera evidently 

 form a natural group that has gradually branched off from 

 a more primitive percoid ancestry, and has broken up into 

 many genera — about 50 — a few of the more percoid of 

 which still inhabit freshwaters, a few others are brakish 

 inhabitants, but by far the most abundant and most highly 

 evolved genera are now marine. 



Accepting the number and nature of the fin-rays as a 

 helpful guide to the explanation of progressive structural 

 advance, it may be said that the existing genera Morone, 



