ACANTIIOPTERYGII. 329 



and cceca generally numerous, constitute almost all that can 

 be said in a general way respecting these fishes, and, never- 

 theless, they all have a sort of family likeness which does not 

 abandon them in any of their modifications, so that they form 

 what botanists would term a family by series or by transition. 

 The majority, however, have the sides of the tail carinated, or 

 armed with scales, or with shields, which are themselves 

 carinated ; or the last rays of the second dorsal, or of the anal, 

 are free ; or the spinous rays of the first want the membrane 

 which should unite them. Frequently the caudal fin is of a 

 remarkable dimension and vigour. In most of them also the 

 first spinous rays of the anal are separated from the rest of this 

 fin, and form a small and distinct one. But none of these 

 characters is common to them all ; and the transition proceeds 

 so far as to approximate them on the one hand to the family 

 of the tsenioides, and on the other to that of the acanthuri. 

 In a word, no group of acanthopterygians better proves than 

 the present, that this order, immense in the number of genera 

 and species which it embraces, constitutes at bottom but a 

 single family, and that its divisions are by no means separated 

 by such distinctions as those of many others. 



It is possible, however, to find in the midst of this family of 

 scomberoides certain groups or tribes better determined than 

 the family itself, which has been done by MM. Cuvier and 

 Valenciennes. 



To the first of these tribes belong the most known and the 

 most useful fishes of this family, the tunnies, the germons, 

 the mackerel, which traversing the seas in numerous shoals, 

 and capable of being procured in various ways, give rise to 

 great fisheries which occupy a very considerable portion of 

 labour and capital. Their fusiform bodies, their large and 

 vigorous caudal, their tail contracted, and more or less cari- 

 nated, make them excellent swimmers, and all their habits 

 are in conformity with this organization. 



