206 Adaptations of Fishes 



a large semitropical genus (Paralichthys) of wide range have 

 from 35 to 41 ; while the tropical forms have from 35 to 37. 



In the group of turbots and whiffs none of the species really 

 belong to the northern fauna, and the range in numbers is from 

 35 to 43. The highest number, 43, is found in a deep-water 

 species (Monolene], and the next, 40, in species (Lepidorhombus, 

 Orthopsetta) which extend their range well toward the north. 

 Among the plaices, which are all northern, the numbers range 

 from 35 to 65, the higher numbers, 52, 58, 65, being found in 

 species (Glyptocephalus) which inhabit considerable depths in 

 the arctic seas. The lowest numbers (35) belong to shore 

 species (Pleuronickthys) which range well toward the south. 



Spiny-rayed Fishes. Among the spiny-rayed fishes the facts 

 are more striking. Of these, numerous families are chiefly or 

 wholly confined to the tropics, and in the great majority of 

 all the species the number of vertebrae is constantly 24, 10 in 

 the body and 14 in the tail (10 + 14). This is true of all or 

 nearly all the Berycidaz, Serranidoz, Sparida, Sci&nidce, Chceto- 

 dontidaz, Hcemulidce, Gerridcs, Gobiida, Acanthuridce , Mugilidce, 

 Sphyrcenidce, Mullidce, Pomacentridcs, etc. 



In some families in which the process of reduction has gone 

 on to an extreme degree, as in certain Plectognath fishes, there 

 has been a still further reduction, the lowest number, 14, exist- 

 ing in the short inflexible body of the trunkfish (Ostraciori), in 

 which the vertebral joints are movable only in t^e base of the 

 tail. In all these forms the process of reduction of vertebras 

 has been accompanied by specialization in other respects. The 

 range of distribution of these fishes is chiefly though not quite 

 wholly confined to the tropics. 



Thus Batistes, the trigger-fish, has 1 7 vertebras ; Monacanthus 

 and Alutera, foolfishes, about 20; the trunkfish, Ostracion, 14; 

 the puffers, Tetraodon and Spheroides, 18; Canthigaster, 17; 

 and the headfish, Mola, 17. Among the Pediculates, M alike 

 and Antennarius have 17 to 19 vertebras, while in their near 

 relatives, the anglers, Lophiidcs, the number varies with the 

 latitude. Thus, in the northern angler, Lophius piscatorius , 

 which is never found south of Cape Hatteras, there are 30 ver- 

 tebras. In a similar species, inhabiting the north of Japan (Lo- 

 phius litulon), there are 27. In another Japanese species, ranging 



