=The Pipefishes: Syngnathidæ.=—The _Syngnathidæ_ are very long and slender fishes, with neither spinous dorsal, nor ventral fins, the body covered by bony rings. Of the pipefish, _Syngnathus_, there are very many species on all northern coasts. _Syngnathus acus_ is common in Europe, _Syngnathus fuscum_ along the New England coast, _Syngnathus californiense_ in California, and _Syngnathus schlegeli_ in Japan. Numerous other species of _Syngnathus_ and other genera are found further south in the same regions. _Corythroichthys_ is characteristic of coral reefs and _Microphis_ of the streams of the islands of Polynesia. In general, the more northerly species have the greater number of vertebræ and of bony rings. _Tiphle tiphle_ is a large pipefish of the Mediterranean. This species was preceded by _Tiphle albyi_ (_Siphonostoma_) in the Miocene of Sicily. Other pipefishes, referred to as _Syngnathus_ and _Calamostoma_, are found as fossils in Tertiary rocks. =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. [Illustration: FIG. 188.—_Solenostomus cyanopterus_ Bleeker. Misaki, Japan. ] [Illustration: FIG. 189.—Sea-horse, _Hippocampus hudsonius_ Dekay. Virginia. ] No fossil sea-horses are known. 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: