SPINY-RAYED FISHES. 63 



their head thick. The dentition is feeble. Some bones of the 

 head are armed, and a bony stay connects the preopercular spine 

 with the infraorbital ring. The "Bull-heads," or "Millers'-thumbs " 

 {Coitus), are small fishes from the shores and fresh waters of 

 Northern Europe, Northern Asia, and North America. The 

 common British Miller's-thumb (C. gobio) is exclusively confined to 

 fresh waters ; two marine species are common on our coasts (C. scor- 

 pius and bubalis), whilst a fourth (C. lilljeborgii) inhabits deeper 

 water on the North-British coasts. The Gurnards (Trigla), of which 

 seven species occur on the British coast, are principally characterized 

 by the free finger-like pectoral appendages which serve as organs of 

 locomotion as well as of touch. The Flying-Gurnards (Dactylo- 

 pterus), of which three species are known, are very abundant in the 

 Mediterranean, the tropical Atlantic, and Indo-Pacific. They and 

 the "Flying-Herrings" (Exoccetus) are the only fishes which are 

 enabled by their long pectoral fins to take flying leaps out of the 

 water, and deserve the name of " Flying-fishes " ; when young 

 their pectorals are much shorter, and consequently they are unable 

 to raise themselves out of the water. 



The Trachinidce (Case 8) have the body elongate, naked, or [Case 8. 

 covered with scales, and the spinous portion of the dorsal fin 

 always much shorter than the soft. The Weevers (Trachinus) are 



Fier. 47. 



The Weever (Trachinus draco); with separate view of opercular spine. 



common fishes on the European coasts, and but too well known to 

 all fishermen. Wounds by their dorsal and opercular spines are 

 much dreaded, being extremely painful, and sometimes causing 

 violent local inflammation. In the absence of any special poison- 

 organ, it is very probable that the mucous secretion in the vicinity 

 of the spines has poisonous properties. The dorsal spines as well 



