CENTRONO'TUS, a genus of Fishes belonging to the section A canthopteryyii and family Seorriberktre. In this genus the spines; which in most of the Acanthopterygians form the anterior dorsal fin, are free or unconnected by membrane; they have all ventral fins.
The. above characters are common to a large number of species of the Sconiberidm, and hence it has been thought convenieut to seize some minor distinctions for the purpose of dividing the genus Centronotus into several sub-genera. In Cuvieea 'Lague Animal' they are as follows :--Sub-genus Naueratee, or those in which the body is elongate ; the tail carinated at the sides, and which have two i free spines before the anal fin. To this subgenus belongs the Pilot Fish (Naucrates ductor), which is well known for its habit of following vessels to a considerable distance in order to feed upon what is thrown overboard; and it is under such circumstances that this fish has been occasionally met with on the British coast. It is about a foot in length, and of a bluish-gray colour, with five broad bands of deep violet. Its shape is something like that of the mackerel, but less tapering towards the head and tail. The pectoral and ventral
fins are of moderate size, the latter very close together; the dorsal fin commences about midway between the head and the tail, and contiuues almost to the latter part ; anterior to the dorsal fin there are three free spines : the tail is forked.
Elacales is another sub-genus. The species have nearly the form of the one last mentioned, but differ in the head being depressed, the tail not earinated, and there being no free spines before the mud fin. Tho next sub-genus, Lichia, has free spines before the dorsal and anal fins, and the tail not earinated at the aides. In front of the dorsal spines there is a single one laid flat and pointing fonvards. The &ember amia of Linnrena, a large fish upward*, of 4 feet in length, which inhabits the Mediterranean, belongs to this section. There are two other apecies known from the same locality ; the one hero mentioned is distinguished by the lateral line being much curved and forming all S. The last sub-genus, Trachinotus, damn chiefly from Lichia in having the profile of the body deeper, and the dorsal and anal fins longer and more tapered.