Adaptations of Fishes 209 



100 or more; Lunipenus, 79; Pholis, 85; Lycodes, 112; Gyninelis, 

 93. Lycodes and Gymnelis have lost all the dorsal spines. 



In the cod family {Gadidcc) the number of vertebrae is usu- 

 ally about 50. The number is 51 in the codfish (Gadus callarias), 

 58 in the Siberian cod {Elegiims navaga), 54 in the haddock 

 (Melanogrammus ceglifinus), 54 in the whiting (Merlangus mer- 

 langiis), 54 in the coalfish {PollacJiins virens), 52 in the Alaskan 

 coalfish {Theragra cJialcogramma) , 51 in the hake {Merlitcciiis 

 merliiccius). In the burbot {Lota lota), the only fresh-water 

 codfish, 59; in the deep-water ling (Molva niolva), 64; in the 

 rocklings (Gaidropsarns), 47 to 49. Those few species found 

 in the Mediterranean and the Gulf of Mexico have fewer fin-rays 

 and probably fewer vertebrse than the others, but none of the 

 family enter warm water, the southern species living at greater 

 depths. 



In the deep-sea allies of the codfishes, the grenadiers or 

 rat-tails (ALicrouridcr), the numbers range from 65 to 80. 



Fresh-water Fishes. — Of the families confined strictly to 

 the fresh waters the great majority are among the soft-rayed or 

 physostomous fishes, the allies of the salmon, pike, carp, and 

 catfish. In all of these the vertebra are numerous. A few 

 fresh-water families have their affinities entirely with the more 

 specialized forms of the tropical seas. Of these the Centrarchidcc 

 (comprising the American fresh-water sunfish and black bass) 

 have on the average about 30 vertebra, the pirate perch 29, 

 and the Percidcs, perch and darters, etc., 35 to 45, while the 

 SerranidcB or sea-bass, the nearest marine relatives of all these, 

 have constantly 24. The marine family of damsel-fishes (Poina- 

 centrida) have 26 vertebras, while 30 to 40 vertebras usually 

 exist in their fresh-water analogues (or possibly descendants), 

 the Cichlido', of the rivers of South America and Africa. The 

 sticklebacks {Gasterosteidce), a family of spiny fishes, confined 

 to the rivers and seas of the north, have from 31 to 41 vertebras. 



Pelagic Fishes. — Among the free-swimming or migratory 

 pelagic fishes, the number of vertebra; is usually greater than 

 among their relatives of local habits. This fact is most evident 

 among the scombriform fishes, the allies of the mackerel and 

 tunny. All of these belong properly to the warm seas, and the 

 reduction of the vertebra; in certain forms has no evident rela- 



