TELEOSTEI. 387 



Sub-order C. Acanthopteri. — This sub-order is charac- 

 terised by the fact that one or more of the first rays in the 

 fins are m the form of true, unjointed, inflexible, "spiny" rays. 

 The exoskeleton consists, as a rule, of ctenoid scales. The 

 ventral fins are generally beneath or 'in advance of the pectorals, 

 and the duct of the swim-bladder is invariably obliterated. 



This sub-order comprises two families : — 



a. The Pharyngognathi, in which the inferior pharyp^eal 

 bones are anchylosed so as to form a single bone, which is 

 usually armed with teeth. The family is not of much import- 

 ance, the only familiar fishes belonging to it being the " Wrasses " 

 ( CyclolabridcB). 



b. The Acanthopteri vert, characterised by having always 

 spiny rays in the first dorsal fin, and usually in the first rays of 

 the other fins, whilst the inferior pharyngeal bones are never 

 anchylosed into a single mass. This family includes many 

 subordinate groups, and may be regarded as, on the whole, 

 the most typical division of the Teleostean fishes. It will not 

 be necessary, however, to do more than mention as amongst 

 the more important fishes contained in it, the Perch family 

 (PercidcE), the Mullets {Mugilidm), the Mackerel family {Scom- 

 beridce), the Gurnards (Sderogenidts), the Gobies (Gobiida), the 

 Blennies {BlenniidcB), and the Anglers (Lophiidd). The Per- 

 cidcB form by far the most important member of this group, and 

 are distinguished by having ctenoid scales, the operculum and 

 prai-operculum variously armed with spines, teeth on the vomer 

 and palate as well as on the jaws, and the branchiostegal rays 

 from five to seven in number. 



Sub-order D. Plectognathi. — This sub-order is charac- 

 terised by the fact that the maxillary and premaxillary bones 



Fig. 145. — Ostraciontidse. Homed Trunk-fish (Ostracion comutvs). 



are immovably connected qn each side of the jaw. The endo- 

 skeleton is only partially ossified, and the vertebral columu 

 often remains permanently cartilaginous. The exoskeleton is 

 18 



