324 PISCES. 



the bones of the head and gill-covers : generally 

 one dorsal, with simple slender rays: the other 

 fins often wanting. 



66. SYNGNATHUS Snout prolonged into a tube; 

 mouth placed at the extremity, and cleft nearly vertically : 

 body very much elongated, slender, and of nearly equal 

 thickness throughout : gill-opening towards the nape : ven- 

 trals always wanting. 



67. HIPPOCAMPUS. Snout tubular; the mouth 

 placed at the extremity : trunk of the body laterally com- 

 pressed, and more elevated than the tail : the joints of the 

 squamous plates raised in ridges ; the projecting angles 

 spinous : ventrals, and also caudal, always wanting. 



in. PLECTOGNATHL Jaws incomplete; 

 maxillary firmly attached to the side of the 

 intermaxillary, which alone forms the jaw ; 

 palatine arch united to the cranium by suture, 

 and immoveable : branchiae with the pectina- 

 tions continuous ; opercle and rays concealed 

 beneath the skin; external aperture a simple 

 cleft. 



ORDER IV. GYMNODONTES. 



No true teeth ; but the jaws covered with a lamellated 

 substance resembling ivory, either entire, or divided 

 in the middle by a suture : opercle small ; branch- 

 iostegous rays five on each side; both deeply 

 concealed. 



