116 TEMPERATURE AND FLSH VERTEBRAE JORDAN. 



members being found on the sandy shores of all zones, renders it es- 

 pecially important in the present discussion. The other Anacanthine 

 families are chiefly contined to the cold waters or to the depths of tho 

 seas. 



In the Cod famil.v* (GaduUv) the number of vertebrte is usually about 

 50, and in their deep-sea allies, the grenadiers! or rat-tails, the numbers 

 range from 65 to 80. 



FRESH-WATER FISHES. 



Of the families confined strictly to the fresh waters the great ma- 

 jority are among the soft- rayed or physostomous fishes, the allies of the 

 salmon,! pike, carp, and catfish. In all of these the vertebne are 

 numerous. A few fresh-water families have their affinities entirely 

 with the more specialized forms of the tropical seas. Of these the Cen- 

 trarchidce (comprising the American freshwater sun-tisli§ and black ! 

 bass||) have on the average about 30 vertebne, the pirate perch^ UO, and 

 the perch** family, perch and darters, etc., 35 to 45, while the ^erranidce 

 or sea bass, the nearest marine relatives of all these, have constantly 

 24. The marine family of Deuioisellestt have 26 vertebnie, while 30 lo 

 40 vertebrje usually exist in their fresh-water analogues (or possibly 

 descendants), the Gichlidcv, of the rivers of South America and Atrica. 

 The sticklebacks,!! a family of spiny fishes, confined to the rivers and 

 seas of the north, have from 31 vertebme to 41. 



PELAGIC FISHES. 



It is apparently true that among the free swimming, or migratory 

 pelagic fishes, the number of vertebne is greater than among their rela- 

 tives of local habits. This fact is most evident among the Scombri loi in 

 fishes, the allies of the mackerel and tunny. All of these belong jfrop 

 erly to the warm seas, and the reduction of the vertebne in certain lonns 

 has no evulent relation to the temperature, though it seems to be relatcl 

 in some degree to the habits of the species. Perhaps the retention of 

 many segments is connected with that strength and swiftness in the 

 water for which the mackerels are i)reeminent. 



* Fifty-one in the codfish {Gadus callarias), 58 in the Siberian cod (Pleurof/adiis 

 navafja), 54 in the haddock {Melanoyrammua (vyUfinus), 54 m the whiting {MerltiiK/tis 

 mtrlaiifiiis), 54 in the coal-fish (PoUachiiis virens), 5xJ in the Alaskan coal-fish (I'liJIa- 

 chius chalcoi/rammiis), 51 in the hake i Merhiccins merluccius). In the burbot (Lota 

 lota), the only fresh-water codfish, 59; in the deep-water ling {Molva molva), (54 ; iu 

 the rocklings (Gatdropsarns), 47 to 49. Those few species found in the Mediter- 

 ranean and the Gnlf of Mexico have fewer fin rays and probably fever vertebra? than 

 the others, but none of the family cuter warm water, the southern species- living air 

 greater depths. 



t Macrurid(r. 



t Cyprinido', Salinonidce, Emoidw, Characiuid(v, Cifprinodontido:, Silitridw, etc. 



^ Lepomis. \\ Microptcrns. 



H Jphredoderidw. ** Percidw. 



i\ Pomacentrida. tt Gasterosteidce. 



