488 MANUAL OF ZOOLOGY. 



This sub-order comprises two families : 



a. The Pharyngognathi, in which the inferior pharyngeal bones are an- 

 chylosed so as to form a single bone, which is usually armed with teeth. 

 The family is not of much importance, the only familiar fishes belonging 

 to it being the "Wrasses" (CyclolabridcE). 



b. The Acanthopteri veri, 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 import- 

 ant fishes contained in it, the Perch family (Percida), the Mullets (Mugi- 

 lidce), the Mackerel family (Scomberidtz), the Gurnards (Sclerogenidce}, the 

 Gobies (Gobiidce), the Blennies (Blenniida:}, and the Anglers (Lopkiida). 

 The Percidce form by far the most important member of this group, and are 

 distinguished by having ctenoid scales, the operculum and prse-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 prsemaxillary 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 (Ostraci- 

 ontidce, 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 (fialis- 

 tidce) and the Globe-fishes (Gymnodontidce). 



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

 portant group, mainly characterised by the peculiar structure 

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

 arches, instead of the comb-like plates of the typical Bony Fishes. 

 The endoskeleton is only partially converted into bone, and the 

 exoskeleton, by way of compensation, consists of ganoid plates. 

 The swim-bladder is destitute of an air-duct. 



The singular Sea-horses (Hippocampidcc), now kept in most of our large 

 aquaria, belong to this sub-order, but the only point about them which re- 

 quires notice is the curious fact that the males in this family are provided 

 with a sort of marsupial pouch, into which the eggs are placed by the 

 female, and to which the young, when hatched, can retire if threatened 

 by any danger. This singular cavity is only found in the males, and is 

 situated at the base of the tail. More familiar than the Sea-horses are the 

 Pipe-fishes (Syngnathid<z\ of which one species occurs commonly on our 

 shores. 



