TELEOSTEI. 363 



face, the sides are often looked upon as the dorsal and ventral 

 surfaces of the body. This, however, is erroneous, as they are 

 shown by the position of the paired fins to be truly the lateral 

 surfaces of the body. 



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 in 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 pharyngeal 

 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 " ( Cydolabridce). 



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 (Mugilidce), the Mackerel family (Scom- 

 berid<z\ the Gurnards (Sclerogenida), the Gobies (Gobiidce), the 

 Blennies (Blenniidce), and the Anglers (Lophiidce). 



SUB-ORDER D. PLECTOGNATHI. This sub-order is charac- 

 terised by the fact that the maxillary and premaxillary bones 

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

 skeleton is only partially ossified, and the vertebral column 

 often remains permanently cartilaginous. The exoskeleton is 

 in the form of ganoid plates, scales, or spines. The ventral 

 fins are generally wanting, and the air-bladder is destitute of a 

 duct. 



The most remarkable fishes of this section are the Trunk- 

 fishes (Ostraciontidtz, fig. 137), in which the body is entirely 

 enclosed, with the exception of the tail, in an immovable case, 

 composed of large ganoid plates, firmly united to one another 

 at their edges. 



Besides the Trunk-fishes, this section also includes the File- 

 fishes (Balistidce) and the Globe-fishes (Gymnodontida). 



SUB-ORDER E. LOPHOBRANCHII. This is a small and 

 unimportant group, mainly characterised by the peculiar struc- 

 ture of the gills, which are arranged in little tufts upon the 



