266 FISHES. 



Shore fish also in the Mediterranean, at least in its adult 

 state. Ophidium and Fierasfer appear now besides Ammo- 

 dytes. As the Gadoids decrease, so the Pleuronectidce increase, 

 the genera of the Mediterranean district being Rhomhus, 

 Phrynorhombus, Arnoglossus, Citharus, Bhomboidichthys, Pleu- 

 roTiectes (a northern genus not extending farther southwards), 

 Solea, Synajotura, and Ammopleurops. 



The variety of Physostomes is small ; the foUowuig only 

 being superadded to those of the British district : — Saurus (a 

 tropical genus), Aulopus ; CongromiUTo&na, Heteroconger, Myrus, 

 Ophichihys, Murcena. 



The Lophobranchs are more numerous in species and 

 individuals than in the British district ; and, besides Syngna- 

 thus and Nerophis, several species of Hippocam'pus are common. 

 Also a few species of Balistes occur. 



Myxine is lost in this district; whilst Branchiostoma is 

 abundant. 



3. The shore fishes of the North American district con- 

 sist, as on the eastern coasts of the North Atlantic, of northern 

 and southern elements ; but they are still more mixed with 

 each other than on the European coasts, so that a boundary 

 line cannot be drawn between them. The affinity to the fauna 

 of the eastern shores is great, but almost entirely limited to 

 the genera composing the fauna of the British district. 

 British genera not found on the American coasts are — 

 Galeus, Scyllium, Chimmra, Mullus, Pagellus, Trigla, Tra- 

 chinus, Zeus, Callionymus. The southern elements of North 

 America are rather derived from the West Indies, and have 

 no special affinity to Mediterranean forms ; very few of the 

 non-British Mediterranean forms extend across the Atlan- 

 tic; instead of a Mediterranean we find a West Indian 

 element. Many of the British species range across the Atlantic, 

 and inhabit in an unchanged condition the northern parts of 



