voi,. xiv-j PKOCEKDINGS OF TIIK NATIONAL MUSEUM. 117 



1891. 



The variations in the nuniberof vertebra' in this prroup UmI Dr.Giinther, 

 nearly 30 years ago, to <livi<le it into two families, the Caraiujida' and 

 ticomhruJa. 



The Caratujidw* are tropical shore fishes, local or migratory to a slight 

 degree. All these have from 24 to 2G vertebrje. In their pelagic rela- 

 tives, the <lol|>hins,t there arc from 30 to 33; in the opahs,:j: 45; in the 

 Brama, 42 ; 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 redn(;tion of the tins. In these the vertebne are 

 correspoiitlingly luimeioiis, the numbers ranging from 100 to 160. 

 I In apparent contradistinction to this rule, however, the pelagic family 

 of swordlishes,^] remotely allied to the mackerels, and with even greater 

 powers of swimming, has the vertebne in normal number, the common 

 sworiltish having but 24. 



THE EELS. 



I The eels constitute a peculiar grouj) of uncertain, but probably soft- 

 rayed, ancestry, in which everything else has been subordinated to 

 muscularity and tlexibility of body. The fins, girdles, gill arches, scales, 

 and membrane bones are all imperfectly developed or wanting. The 



i eel is jierliaps as far from the primitive stock as the most highly " ich- 

 thyized" (ishes, 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 greatly sim])litied as compared with its ancestral forms, 

 but in its eel-like qualities it is, however, greatly specialized. All the 

 eels have vertebra' in great numbers. As the great majority of the 



, species are tropical, and as the vertebne in very few of the deep-sea 

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



, of their vertebne to the temperature. 



j It is evident that the two families most decidedly tropical in their 

 distribution, the morays** and the snake eels,tt liave diverged farthest 

 from the primitive stock. They are most " degenerate," as shown by 

 the re<lu(;tion of their skeleton. At the same time they are also most 



decidedly "eel-like," and in some respects, as in coloration, dentition, 



I 



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



t Coijiitlui'iKt. } Lampris. 



^ Scomhridd'. The mackerel (Scomher scomhrits) has 31 vertebrjp : the chub mackerel 

 {Scomber coIIoh), 31 ; the tiiuuy (Albaeota ihi/niiHs), :?9; the long-finued albacore (Alba- 

 cora aJalouija), 40; thebonito (Sarda mrda), 50; the Spanish mackerel (Scomberomorus 

 mdculutits), 45. 



II Trichiiirida; : Aphanopus, lOl vertebne; Lepidopus, 112; Trichtn-us, 159. 



II Xipltiidd . 



" Muianidii'. Amoug the morays, Murcrna Helena has 140 ; Oymnothorax mcleafirw, 

 120; G.undultttus^V^Q; G.vi<>nnfia,l4^i; G.eoncolor,!'^^; Echidna catenala,lU] ; E.neb- 

 M/o«tt, 142; K. zebra, I'^^y. In other families the true eel, Anguilla anguilla, has 115; 

 the Conger eel, Conger conger, 156; and Murwnesox cinereus, 154. 



ft OphiauridCB. 



