72 CHECK LIST OF THE 



number, the bones of the gill arches also reduced except in Gasterosteidse ; 

 inferior pharyngeals present, not united. Ventral fins abdominal or sub- 

 abdominal, joined to the interclavicle, or else detached from it through 

 partial atrophy of the shoulder girdle. Mouth bounded above by premax- 

 illaries only ; shoulder girdle simple in structure. Basis of cranium simple 

 and without tube ; four anterior vertebrae more or less elongate ; snout 

 usually more or less produced, the small mouth at its end. 



Family GASTEROSTEID^^i. (The Sticklebacks.) 



Body more or less fusiform, somewhat compressed, tapering behind 

 to a slender caudal peduncle. Head moderate, the anterior part not greatly 

 produced, but all the bones of the suspensory apparatus somewhat leng- 

 thened. Mouth moderate, with the cleft oblique, the lower jaw prominent ; 

 maxillary bent at right angles and overlapping the prernaxillary at corner 

 of mouth. Teeth sharp, even, in a narrow band in each jaw ; no teeth on 

 vomer or palatines ; premaxillaries protractile. Preorbital rather broad ; 

 suborbital plate large, often covering the anterior part of the cheeks, form- 

 ing a connection with the preopercle. Branchiostegals three. Gill mem- 

 branes broadly joined, free from the isthmus, or not ; gill rakers moderate 

 or rather long. Opercles unarmed. Skin naked or with vertically oblong 

 bony plates ; no true scales. Dorsal fin preceded by two or more free 

 spines ; anal similar to soft dorsal, with a single spine ; ventral fins sub- 

 abdominal, consisting of a stout spine and one or two rudimentary rays. 

 Middle or sides of belly shielded by the pubic bones. Pectorals rather 

 short, unusually far behind the gill opening, preceded by a quadrate naked 

 area which is covered with shining skin. Caudal fin narrow, usually lun- 

 ate. Air bladder simple ; a few pyloric ca?ca. Vertebrce, thirty to thirty- 

 five ; anterior vertebrae little enlarged. Small fishes inhabiting the fresh 

 waters and arms of the sea, noted for their pugnacity. 



They are exceedingly destructive of the spawn and fry of larger 

 fishes. 



Most of the Sticklebacks build elaborate nests, which the male fish 

 defends with much spirit. The species are extremely variable, being appar- 

 ently readily affected by changes in surroundings. 



Genus EUCALIA. (Brook Sticklebacks.) 



Fresh-water Sticklebacks, feebly armed ,the skin not mailed, the dorsal 

 spines few and nondivergent ; the gill membranes forming a free fold 

 across the isthmus ; pubic bones fully united. One species known. 



