GILL-COVER OF THE SILURID^ 57 



on being seized by one of the crew, elicited from 

 him the exclamation, Tliat he had lost the use of 

 his hands and arms; another sailor, on touching it 

 with his feet, received a shock through his leg. 

 This fish, like the Torpedo, does not require to be 

 very large ere it can inflict its shocks : M. Prieur 

 assuring us, that a specimen at Senegal, which was 

 only seven inches long, inflicted very powerful 

 ones. 



Before leaving the family of the Silurida^, it may 

 be worth while to mention a remarkable anomaly 

 which exists in their Gill-covers, and which, we 

 believe, was first pointed out by M. Yalenciennes. 

 It is, that whereas in nearly the whole class of 

 fishes the gill-cover almost uniformly consists of 

 four osseous pieces, in this family it not less inva- 

 riably consists of three only. According to this 

 distinguished Naturalist, all the Siluridae want the 

 subopercidum ; and this anatomical fact is unques- 

 tionably, according to him, one of the most curious 

 which is met y\Aih in the comparative anatomy of 

 fishes. In this class, he remarks, whose species 

 are so numerous, we find a constancy in the respi- 

 ratory apparatus, both as it regards the form and 

 composition of the organ, such as the importance of 

 the function performed by these parts would lead us 

 to expect. When, then. Nature exhibits these ex- 

 ceptions which mock our artificial arrangements, 

 they are generally found very much isolated; and it 

 is usually a single species only which presents us 

 with what is styled an anomaly. Here, however, 



