FAMILIES OF THE APODAL ORDER, 215 



which, alsOj we suspect some of Gymnarchi are natu- 

 rally allied. 



(187.) Our general sketch of this order must be very 

 brief; for, as we have not space for a lengthened expo- 

 sition of every family, we shall only dwell upon those 

 which more especially seem to require elucidation ; and 

 the popular history of the eels, and other well-known 

 fishes belonging to this group, however interesting, 

 is not exactly suited to the nature of these volumes. 

 We shall therefore at once proceed to the natural families 

 of which the order appears to be composed, referring the 

 reader to the general synopsis for the characters of the 

 minor divisions. 



(188.) The eels appear to arrange themselves into 

 two divisions : the one_, which we designate the Mu- 

 rcenidce^ having two branchial spiracles in their ordinary 

 position ; and the Sphagebranchidce, or sea eels, where 

 the branchial spiracles are either close together or united 

 into one, and in both cases are placed under the throat. 

 These we denominate the typical groups. The three 

 aberrant depart more or less from this structure, and 

 each assumes some of the characters of that particular 

 order to which it leads : thus, the Gymnarchidce have 

 the head and body compressed, as in ordinary fishes, 

 and the scales are more developed than in the other di- 

 visions ; because this group, as it appears, leads to the 

 acanthopterygious order. The Petromyzonidcs, or lam- 

 preys, have the skeleton almost obsolete; the body Vvorm- 

 shaped, and without scales : some of these lead to the 

 Vermes, and others to the cartilaginous order. Lastly, 

 we have the Cyclopteridce, or suckers, characterised by 

 their ventral ring; thus connecting the Gymnarchidcs to 

 the Plectognathes, by means of the lump-fish and the 

 LopMdce, or frog-fish. A few general remarks upon 

 these groups seem to be necessary, because, however 

 nearly we think they are related, they have never before 

 been assembled together. 



(I89.) It will be observed, in our last chapter, 

 that the LophidcB are placed at one extremity of the 



p 4s 



