2790 THE BONY FISHES AND GANOIDS 



Day in regarding the group now to be considered merely as a section of the sub- 

 order which includes all the other spiny-finned fishes. That this is the correct view 

 is proved by the circumstance that in one aberrant genus of perches ( Gerres) some 

 of the species have the lower pharyngeal bones separate, while in others they are 

 united. In the three families constituting the present group there is a single dorsal 

 fin, in which the number of spines and soft rays is nearly equal; while the anal is 

 usually similar in character to the soft dorsal; and the pelvic fins are thoracic in po- 

 sition, and include one spine and five soft rays. 



The first of the families of the present sectional group takes its 

 Pomacentrus 



name from the genus Pomacentrus, which, together with the allied 



genera, includes tropical fishes mainly frequenting the neighborhood of coral reefs 

 and islands, and thus closely resembling the scaly-finned fishes (p. 2710) in their 

 mode of life; a few species of the family range, however, into the seas of the tem- 

 perate zones. As an example of the typical genus, we figure P. scolopsis, from the 

 Malayan seas and Polynesia. As a family these fishes are specially characterized 

 by the presence of false gills and ctenoid scales. In form, the body is more or less 

 short and compressed; there are weak teeth in the jaws but none on the palate, and 

 there is an air bladder. The family is represented by eight genera and considerably 

 over a hundred species; and the genera may be divided into groups, according as to 

 whether all or some of the opercular bones are serrated at the edges or are all sim- 

 ple; Pomacentrus belonging to the intermediate group, in which the preopercular is 

 serrated, while the edges of the other bones of the gill cover are entire. In a fossil 

 state the family is represented by an extinct genus from the middle Eocene deposits 

 of Monte Bolca. Pomacentrus is the largest genus of the family, its representatives 

 ranging over the tropical seas of both Hemispheres. Curiously enough, not only do 

 these fishes resemble the scaly-finned fishes in their mode of life, but they are very 

 similarly colored, so much so, indeed, that in some instances actually the same pat- 

 tern of coloration is common to members of the two families. This, as remarked 

 by Dr. Giinther, is one of many instances showing that the coloration of animals 

 depends to a great extent on their mode of life and natural surroundings. All these 

 fishes are carnivorous, subsisting on various small marine animals; those furnished 

 with compressed teeth probably browsing on the coral polyps. 



... Distinguished from the preceding family by their cycloid scales, the 



wrasses form an extensive group {Labridce*) , many of the members of 

 which may be easily recognized by their greatly thickened lips, sometimes provided 

 with an internal fold; and from this characteristic they derive their German title of lip 

 fishes. False gills are present, and the true gills, three and a half in number on 

 each side. The body is oblong or elongate, and while teeth are present in the jaws 

 they are absent on the palate. In the single dorsal fin the number of spines is usu- 

 ally equal to that of the rays; the anal is similar to the soft dorsal, and an air blad- 

 der is present. Littoral in their habits, the great majority of the wrasses are found 

 in tropical and temperate seas, none occurring within the limits of the polar seas. 

 Rocks and coral reefs are their favorite haunts, most of them feeding chiefly on 

 mollusks and crustaceans, for crushing the shells of which their teeth are specially 

 adapted. In many kinds there is an additional pointed curved tooth at each angle 



