Body mailed with transverse angular plates: snout very much produced, formed by a prolongation of 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 compressed, 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.

Plectognathi

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 pectinations continuous; opercle and rays concealed beneath the skin; external aperture a simple cleft.