2o8 Adaptations of Fishes 



the Cephalacanthidcc (flying gurnards), with but 22. In the 

 deeper waters of the tropics are the Peristeditdcc , with 33 vertebrae, 

 and extending farther north, belonging as much to the temper- 

 ate as to the torrid zone, is the large family of the Triglida: (gur- 

 nards) in which the vertebra; range from 25 to 38. 



The family of Agonidce (sea-poachers), with 36 to 40 vertebrae, 

 is still more decidedly northern in its distribution. Wholly con- 

 fined to northern waters is the great family of the Cottida (scul- 

 pins), in which the A^ertebrae ascend from 30 to 50. Entirely 

 polar and often in deep waters are the LiparididcE (sea-snails), 

 an offshoot from the Cottida, with soft, limp bodies, and the 

 vertebra 35 to 65. In these northern forms there are no scales, 

 the spines in the fins ha^-e practically disappeared, and only 

 tlie anatomy shows that they belong to the group of spiny-rayed 

 fishes. In the Cydoptcrida: (lumpfishes), likewise largely arc- 

 tic, the body becomes short and thick, the back-bone inflexible, 

 ami the vertebras are again reduced to 28. In most cases, as 

 the number of vertebrae increases, the body becomes propor- 

 tionally elongate. As a result of this, the fishes of arctic waters 

 are, for the most part, long and slender, and not a few of them 

 approach the form of eels. In the tropics, however, while 

 elongate fishes are common enough, most of them (always ex- 

 cepting the eels) have the normal number of vertebrae, the greater 

 length being due to the elongation of their individual vertebrae 

 and not to their increase in number. Thus the very slender goby, 

 Gohiondhts oceaniciis, has the same number (25) of vertebras as its 

 thick-set relative Gobiits soporator or the chubby Lophogobins 

 cypruioides. In the great group of blenny-like fishes the facts 

 are equally striking. The arctic species are very slender in form 

 as compared with the tropical blennies, and this fact, caused by 

 a great increase in the number of their vertebra;, has led to the 

 separation of the group into several famiUes. The tropical forms 

 composing the family of Blenniidw have from 28 to 49 vertebra;, 

 while in the arctic genera the numbers range from 75 to 100. 



Of the true Blenniidw, which are all tropical or semi-tropical, 

 Blenniiis has 28 to 35 vertebrae; Salarias, 35 to 38; Lcpisoma, 

 34; Cliniis, 49; Cristiceps, 40. A fresh-water species of Cris- 

 ticeps found in Australia has 46. Blennioid fishes in the arctic 

 seas are Anarrhidias, with 76 vertebrae; Anarrhidithys , with 



