76 NORTHERN ZOOLOGY. 



SCOMBEROIDE.E. 



There are few characters that are common to all the fish of this extensive family ; 

 but as even the most discordant of its members are connected by a continuous 

 series of intermediate forms, it is impossible to separate them, and there is, indeed, 

 a certain family likeness which extends to all, arising principally from the small- 

 ness and thinness of the scales, and the peculiarly soft, smooth aspect of the 

 integuments ; the vertical fins are not scaly ; the opercular bones are destitute of 

 spines or denticulations ; and the pyloric cseca are numerous and often clustered. 

 Most of the Scomberoidese have the sides of the tail simply keeled, or with the 

 keels covered by scale-like plates which are themselves keeled : many have the last 

 rays of the second dorsal and anal fins detached, forming spurious finlets, as they 

 are termed ; others have the spinous rays of the first dorsal destitute of connecting 

 membrane, and capable of moving separately ; very generally the caudal is remark- 

 ably large and powerful, and the tail tapers greatly and is very muscular ; and in 

 the greater part the spinous rays of the anal form a small fin distinct from the soft 

 portion. These characters are not all to be found in any one fish or group, but 

 their various combinations and modifications furnish the means of dividing the 

 family into several tribes, which are capable of being more exactly defined than 

 the family itself. 



In the Jirst tribe, of which the common mackerel is a typical species, the first 

 dorsal is continuous ; but both that fin and the anal are succeeded by spurious 

 finlets, and the tail, though keeled, is unarmed : the body is fusiform, and the 

 vigorous caudal fin gives great natatory power. Lepidopus and TricJdurus are 

 considered as supplementary to this group*, though they want not only the spurious 

 finlets, but even all the soft rays of the dorsal : in other respects they closely 

 resemble Thyrsites and Gempylus, which are legitimate members of the tribe. 



In the Histoire des Poissons, the small tribe of " Espadons " (Xiphidce) follows 

 next. It is characterised by the elongated form of the snout, resembling the 

 flat blade of a sword, a javelin, or spit. The fish composing it are like the Tun- 

 nies in the minuteness of their scales, the keeled tail, the very powerful caudal fin, 

 and in their interior organization. They have a continuous dorsal, the keels of the 



* They are so placed in the Histoire des Poissons, but in the Regne Animal they form the first tribe of the Tsenioidese, 

 or Poissons en ruban. 



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