the reader without his having some knowledge of 

 its relationships and an understanding of its mar- 

 velous structure. 



Nearly forty species of sea-horses are known and 

 are described in the systematic works of ichthyol- 

 ogy. The individuals of the two different sub- 

 families vary in size, ranging from two to twelve 

 inches in length in genera such as Hippocampus, 

 Acentronura, and Phyllopteryx, while in the genus 

 Solenognathus some attain to a length of two feet. 

 These latter forms, however, do not bear much re- 

 semblance to the typical hippocampids; they are 

 more like pipe-fishes, and they are found only off 

 the coasts of Australia and China. 



The species with which this monograph is con- 

 cerned is called Hippocampus hudsonius; it in- 

 habits the whole Atlantic Seaboard from the Gulf 

 of Mexico to the waters of Long Island Sound. It 

 is this species which is so largely represented by 

 popular pictures, public aquarium exhibits, and 

 conventional decorations and ornaments having a 

 marine motif. Its uniqueness in the popular mind 

 undoubtedly lies in its horse-like head; but to the 

 naturalist it is singular because it is the only fish 

 having a prehensile, or grasping, tail. Long ago 



[275] 



