=The Sea-horses: Hippocampus.=—Both fossil and recent forms constitute a direct line of connection from the pipefishes to the sea-horses. In the latter the head has the form of the head of a horse. It is bent at right angles to the body like the head of a knight at chess. There is no caudal fin, and the tail in typical species is coiled and can hardly be straightened out. _Calamostoma_ of the Eocene, _Gasterotokeus_ of Polynesia, and _Acentronura_ of Japan are forms which connect the true sea-horses with the pipefish. _Gasterotokeus_ has the long head and slender body of the pipefish, with the prehensile finless tail of a sea-horse. Most of the living species of the sea-horse belong to the genus _Hippocampus_. These little creatures have the egg-sac of the male under the abdomen. They range from two inches to a foot in length and some of the many species may be found in abundance in every warm sea. Some cling by the tails to floating seaweed and are swept to great distances; others cling to eel-grass and live very near the shore. The commonest European species is _Hippocampus hippocampus_. Most abundant on our Atlantic coast is _Hippocampus hudsonius_. _Hippocampus coronatus_ is most common in Japan. The largest species are _Hippocampus ingens_ of Lower California and _Hippocampus kelloggi_ in Japan. Many species, especially of the smaller ones, have the spines of the bony plates of the body ending in fleshy flaps. These are sometimes so enlarged as to simulate leaves of seaweed, thus serving for the efficient protection of the species. These flaps are developed to an extreme degree in _Phyllopteryx eques_, a pipefish of the East Indies.
FIG. 188.—_Solenostomus cyanopterus_ Bleeker. Misaki, Japan. ]
FIG. 189.—Sea-horse, _Hippocampus hudsonius_ Dekay. Virginia. ]
The following account of the breeding-habits of our smallest sea-horse (_Hippocampus zosteræ_) was prepared by the writer for a book of children's stories:
"He was a little bit of a sea-horse and his name was Hippocampus. He was not more than an inch long, and he had a red stripe on the fin on his back, and his head was made of bone and it had a shape just like a horse's head, but he ran out to a point at his tail, and his head and his tail were all covered with bone. He lived in the Grand Lagoon at Pensacola in Florida, where the water is shallow and warm and there are lots of seaweeds. So he wound his tail around a stem of seaweed and hung with his head down, waiting to see what would happen next, and then he saw another little sea-horse hanging on another seaweed. And the other sea-horse put out a lot of little eggs, and the little eggs all lay on the bottom of the sea at the foot of the seaweed. So Hippocampus crawled down from the seaweed where he was and gathered up all those little eggs, and down on the under side of his tail where the skin is soft he made a long slit for a pocket, and then he stuffed all the eggs into this pocket and fastened it together and stuck it with some slime. So he had all the other sea-horse's eggs in his own pocket.