FAMILIES OF THE MACROLEPTES. 15 



excessively shorty so that the vent is close to the pec- 

 toral fin. This peculiarity, joined to a very long 

 ventral, assimilates them to the apodal order. Each of 

 these divisions are represented by the follow^ing well- 

 known fishes : — the common perch ; the chsetodon ; the 

 common grey mullet ; the surmullet ; and the Ophio- 

 cephalus. 



(12.) The above families appear to form a circular 

 group, which may be traced in the following manner. 

 Commencing with the Percidm with spined opercula, 

 we pass through Holocentrus to Percis, — a singular 

 genus, which, by its fleshy lips and nearly smooth gills, 

 prepares us for the Labridce, which thus connect the 

 Percidce and the ChcBtodonidcB. By means of Clepticus 

 and Gerres, we pass to ChcEtodon and Holocanthus, the 

 two most perfect groups of their family. Diplerodon and 

 Ephippus lead us to the Scicenmcs ; and these, again, to 

 the Sparidcs. Many of these latter genera show an evi- 

 dent affinity to the mullets : in this small family we also 

 include the genus Polynemus, which, in all but its pec- 

 toral processes, is but a slight modification of the form 

 of MugiL The surmullets (^Mullus) appear to follow 

 these; and we again return to the Percidce by means of the 

 Spirohranchidce, where the genera Datnia, Helotes, and Pe- 

 lates of Cuvier, blend into the perches in the most gradual 

 manner. Before exhibiting the analogies which this great 

 circle presents to others, we shall take a short survey of 

 each of the families ; the scientific or technical details 

 of which wiU be found at large in the systematic arrange- 

 ment. 



(13.) The PercidcB, or perches, is the only group in 

 this tribe which contains species inhabiting fresh waters, 

 of which the common perch is a well-known example ; 

 the great majority being marine : with a very few excep- 

 tions, they are all oblong fishes, having the membranes 

 of their fins sub-transparent, and destitute of scales to- 

 wards the base. In all these characters they differ essen- 

 tiaDy from the next family, or the Chcetodonidce, whose 



