SILUBID^. THE ASPBEDINiE. 255 



fin is very long; but in the more typical forms, such as in 

 90 



the true genus Aspredo Art. (fig. 80.), this fin is short. 

 There is but one dorsal fin, which is small, and placed 

 nearest the head; the first dorsal, and the first of the pec- 

 toral rays are generally very strong, and more lengthened 

 than usual, and the barbels or cirri always present, although 

 variable in their number ; the muzzle projects slightly 

 beyond the under jaw, which is transverse. Cuvier 

 observes that the immobility of the operculum is occa- 

 sioned by the pieces which compose it being cemented, 

 as it were, to the tympanic bone and to the pre-oper- 

 culum. These characters apply, more or less, to the fol- 

 lowing genera : — Platystachus Bloch, Astroblepus Humb. 

 (fig- 9^')} and Aspredo of Artedi and Gronovius ; several 



others will doubtless be added, when the subordinate 

 forms in this family are better understood. Now, it 

 will be remembered that we have already designated 

 several genera, equally remarkable with these for the 

 smallness of their eyes^ and their depressed head ; such, 

 for instance, as Cataphr actus, Cydopium, and Cefopsis; 

 but in none of these do we find the depressed body, 



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