236 ACANTHOPTERYGII. 



Eleventh group Acanthopterygii gasterosteiformes. 



Mouth small : anterior. Spinous dorsal fin, when present, composed of 

 isolated spines. Pubic bone attached to the humeral arch, and the ventral fins, 

 if present, abdominal. 



Family, XXVI GASTEROSTEIDiE. 



Branchiostegals three: pseudobranchiae present. Body elongated and com- 

 pressed. Eyes lateral. Cleft of mouth oblique. Villiform teeth in the jaws. 

 Opercular bones unarmed. The first dorsal fin composed of isolated spines. 

 Ventral fins, when present, abdominal and articulated with the pubic bone, 

 each consists of one spine and one soft ray. Scales absent, but sides of the 

 body more or less cuirassed with bony scutes. Air-bladder present. 



Genus I. Gasterosteds, Artedi. 



Centriscus, Klein ; Spinachia, Fleming; Leiurus and Polij acanthus, Swainson; 

 Apeltes and Pygosteus, Brevoort ; Gasterostea and Gastrwa, Sauvage. 



Definition as given to the Family. 



Fleming made Gasterosteus spinachia the type of his genus Spinachia, Swainson 

 of Poly acanthus, and Sauvage of Gastraia ; while G. pungitius forms the type of 

 genus Leiurus, Swainson, Pygosteus, Bi'evoort, and Gasterostea, Sauvage. 



Its name is derived from the words yaan)p, "the belly," and carta, "a 

 bone," which has reference to the expansion of the pubic bone on the lower 

 surface and to which the ventral fins are attached. 



Geographical distribution. Arctic and temperate regions of both hemispheres. 



Sticklebacks are among the smallest forms of our fresh water fishes : and 

 Buckland tells a tale of how one was served out with the afternoon milk at the 

 door of a house in London. The only excuse the vendor had, was to beg pardon 

 for not having strained the water. These fish abound in some of our reservoirs. 

 The construction of nests for the reception of their ova appears to be a generic 

 feature among them, pertaining equally to the marine and fresh water forms. 



These fishes are subject not only to great variations in colour but likewise in 

 structure, either of the plates on the sides or the spines of the fins, and these 

 variations are more frequent in some localities than they are in others. If we 

 investigate the number of species residing in these islands we find them variously 

 stated by the different British ichthyological authors. Some can only perceive 

 three species, two of which are fresh water forms, and these they believe to be 

 subject to many variations in structure. Others would limit nature to one model, 

 and all which fail to exactly agree with what they consider to be the type are by 

 them referred to another species. While a third class of naturalists have gone 

 still further and what are believed varieties by some, or distinct species by others, 

 they would erect into types of genera or sub-genera. It will not, therefore, be a 



