TELEOSTEI. 



167 



fibres of the other without forming a chiasma. The gills are usually 

 comb -shaped, and, as in the Ganoids, lie freely in a branchial cavity 

 under a branchial operculum, to which is added a a branchiostegal 

 membrane, supported by branchiostegal rays. The skeleton is char- 

 acterised by the well separated, usually bony vertebrae, and by the 

 bony skull, beneath which remains of the primitive cartilaginous 

 cranium often persist. The skin is only rarely naked or apparently 

 without scales. In such cases the scales are very small and do not 

 project from the surface ; more frequently bony plates and scutes 

 are present in it, especially behind the head. As a rule the skin is 

 covered by cycloid or ctenoid scales which overlap one another. 



The urinary and genital organs open 

 behind the anus either separately or by a 

 common aperture on a urogenital papilla. 

 [The kidney is dilated in front to form 

 a head-kidney, which, however, is in the 

 adult, sometimes if not always, largely 

 composed of a tissue resembling lymphatic 

 tissue (Balfour). The generative ducts are 

 continuous with the investments of the 

 generative glands in both sexes, and in the 

 male there is no connection between the 

 testis and the kidney.] 



Only a few Teleosteans are viviparous ; 

 they almost all lay small eggs in enormous 

 numbers in protected places. 



Sub-order 1. Lophobranchii. Teleo- 

 steans with armoured skin, elongated 

 tubular snout which is without teeth. 

 The gills are in the form of tufts and 



j.1. -11 TI FIG. 609. Male of Hippocampus 



the gill slits are very narrow. witll the brood . p ouch (Srt). 



Fam. Pegasidae. The body is flattened ; pectoral fins large, spread out like 

 wings ; pelvic fins small. Pegasus volans L., East Indies. 



Fam. Syngnathidae. The body is cylindrical or laterally compressed. The 

 -gill openings narrow, and pectoral fins small ; males with brood-pouches 

 (fig. 609). Syngnatlius acus L., Pipe-fish ; Hippocampus antiquorum Leach., 

 Sea-horse, Mediterranean. 



Sub-order 2. Plectognathi. Globular or laterally compressed 

 Teleosteans, with immovably fused maxilla and prremaxilla, and 

 narrow mouth. The dermal armour is strong and often bears spines. 

 There are usually no pelvic fins. The gills are comb-shaped 



