Gastrotokeus.—Body depressed, the lateral line running along the margin of the abdomen. Shields smooth. Tail shorter than the body. Pectoral fins. No pouch is developed for the ova, which are imbedded in the soft integument of the abdomen of the male.
Gastrotokeus biaculeatus, very common in the Indian Ocean to the coasts of Australia.
Solenognathus.—Body compressed, deeper than broad. Shields hard, rugose, with round or oval interannular plates; and without elongate processes. Tail shorter than the body. Pectoral fins.
Three species, from the Chinese and Australian Seas; they are the largest of Lophobranchs, S. hardwickii, attaining to a length of nearly two feet.
Fig. 309.—Phyllopteryx eques.
Phyllopteryx.—Body compressed, or as broad as deep. Shields smooth, but some or all of them are provided with prominent spines or processes on the edges of the body; some of the processes with cutaneous filaments. A pair of spines on the upper side of the snout and above the orbit. Tail about as long as the body. Pectoral fins. The ova are imbedded in soft membrane on the lower side of the tail, without a pouch being developed.
Three species from the coasts of Australia. The protective resemblances with which many Lophobranchs are furnished, attain to the highest degree of development in the fishes of this genus. Not only their colour closely assimilates that of the particular kind of seaweed which they frequent, but the appendages of their spines seem to be merely part of the fucus to which they are attached. They attain a length of 12 inches.
Hippocampus.—Trunk compressed, more or less elevated. Shields with more or less prominent tubercles or spines. Occiput compressed into a crest, terminating at its supero-posterior corner in a prominent knob (coronet). Pectoral fins. The males carry the eggs in a sac at the base of the tail, opening near the vent.
A singular resemblance of the head and fore part of the body to that of a horse, has given to these fishes the name of “Sea-horses.” They are abundant between and near the tropics, becoming scarcer in higher latitudes. Some twenty species are known, some of which have a wide geographical range, as they are often carried to great distances with floating objects to which they happen to be attached.—Acentronura is a genus closely allied to Hippocampus.