Tetnperature and Vertebra 27 



The Caraiigidce'-^ are tropical shore fishes, local or migratory 

 to a slight degree. All these have from 24 to 26 vertebrae. 

 In their pelagic relatives, the dolphins, f there are from 30 to 

 33; in the opahs,| 45 ; in the Brama, a,i ; while the great 

 mackerel family, § all of whose members are more or less 

 pelagic, have from 31 to 50. 



Other mackerel-like fishes are the cutlass || fishes, which 

 approach the eels in form and in the reduction of the fins. 

 la these the vertebrse are correspondingly numerous, the 

 numbers ranging from 100 to 160. 



In apparent contradistinction to this rule, however, the 

 pelagic family of swordfishes,^ remotelj^ allied to the mack- 

 erels, and with even greater powers of swimming, has the 

 vertebrae in normal number, the common swordfish having 

 but 24. 



The Eels. — The eels constitute a peculiar group of uncertain, 

 but probably soft-rayed, ancestry, in which everything else has 

 been subordinated to muscularity and flexibility of body. The 

 fins, girdles, gill arches, scales, and membrane bones are all 

 imperfectly developed or wanting. The eel is perhaps as far 

 from the primitive stock as the most highly "ichthyized" 

 fishes, but its progress has been of another character. The 

 eel would be regarded in the ordinary sense as a degenerate 

 type, for its bony structure is greatl}^ simplified as compared 

 with its ancestral forms, but in its eel-like qualities it is, how- 

 ever, greatly specialized. All the eels have vertebrae in great 

 numbers. As the great majority of the species are tropical, 

 and as the vertebrae in very few of the deep sea forms have 

 been counted, no conclusions can be drawn as to the relation 

 of their vertebrae to the temperature. 



*Pampanos, amber fishes, pilot fishes, cavallas, etc. 



t Coryphcena. % Lampris. 



\Scornbridce. The mackerel (Scomber scombrus) has 31 vertebra; 

 the chub mackerel (Scomber colzas), 31; the tunny (Albacora thynnus), 

 39; the long-fiuued albacore (Albacora alalongd), 40; the bonito (Sarda 

 sarda), 50 ; the Spanish mackerel (Scomberomorus maculatus), 45. 



\\ Trickiui'ida; : Aphanopus, loi vertebra; Lepidopus, 112; Tri- 

 churus, 159. 



\ Xiphiidce. 



