Fam. 34. Pomacentridae.—A subocular shelf; entopterygoid present; palate toothless; teeth conical or incisor-like; lower pharyngeals completely united into one bone. Vertebrae with transverse processes from the fourth or fifth; ribs inserted on the transverse processes, when these are present. A single nostril on each side. Gill-membranes free from the isthmus; 5 to 7 branchiostegal rays; gills 3½; pseudobranchiae present. Dorsal fin elongate, with numerous strong spines; anal with 2 spines only. Ventral fins with 1 spine and 5 soft rays.
Small fishes of the tropical and warm seas, resembling the Chaetodontidae in form and mode of life, likewise usually of brilliant coloration; in structural characters intermediate between the Cichlidae and the Labridae. They feed chiefly on small marine animals, but the species with incisor-like teeth are entirely or mainly herbivorous. Over 150 species are known.
Principal genera: Heliastes, Azurina, Amphiprion, Premnas, Dascyllus, Pomacentrus, Glyphidodon, Microspathodon.
The family is supposed to be represented in the Upper Eocene and Lower Miocene of Italy by the extinct genus Odonteus.
Fam. 35. Labridae.—No subocular shelf; entopterygoid present; palate toothless; anterior teeth of the jaws usually strong and canine-like, lateral teeth often soldered at the base; lower pharyngeals completely united into one bone, with conical or tubercular teeth. Vertebrae with transverse processes from the third; all the ribs attached to the transverse processes. Lips thick. Two nostrils on each side. Gill-membranes free or joined to the narrow isthmus; 5 or 6 branchiostegal rays; gills three and a half; pseudobranchiae present. Dorsal fin elongate, with numerous, usually slender, spines. Ventral fins with 1 spine and 5 soft rays.
The "Wrasses" form a large family of mostly brilliantly coloured marine fishes, inhabiting all the tropical and temperate coasts. Their regime is partially herbivorous, partially carnivorous. About 400 species are known. Principal genera: Labrus, Tautoga, Malacopterus, Ctenolabrus, Chaerops, Platychaerops, Heterochaerops, Labrichthys, Cossyphus, Cirrhilabrus, Chilinus, Epibulus, Anampses, Platyglossus, Novacula, Julis, Gomphosus, Chilio, Coris.
Fig. 412.—Upper and lower pharyngeal bones of Labrus maculatus.
Some of the members of this family have been observed to build nests for the protection of their eggs and young. These nests, in the European Labrus, are made of seaweeds, zoophytes, corals, broken shells, etc., and are the work of both the male and the female.[[719]] It is also in this family that sleep was first observed in fishes, and this has been fully verified by Möbius[[720]] on Labrus rupestris in an aquarium, the fish seeking a sleeping place at night and laying itself down to rest on one side.
As first pointed out by Günther, the Labridae found in temperate regions have a higher number (30 to 41) of vertebrae than those inhabiting the tropics (23 to 29), a rule which applies more or less to other families of Acanthopterygians. Remains of Labrus and Julis occur in the Eocene and Miocene of Europe. An allied fossil genus, Labrodon, is represented by numerous species in Tertiary beds of Europe and North America. Phyllodus, Egertonia, Platylaemus, and Pseudosphaerodon, from the Eocene and Miocene, are referred, with doubt, to this family.