GENERA OF ATHERINOPSIN^ 15 



2. Head and adjacent part of trunk naked; body sharply compressed; 

 belly with a fleshy keel ; head abruptly truncated posteriorly ; the gill- 

 slits behind the first much restricted ; anal fin with about 23 soft rays. 



Surf along shores of western Pacific and Australia 19. Iso. 



Atherinopsin^ : Premaxillaries broadly dilated posteriorly (not greatly 

 dilated in Labidesthes and Xenatherina) ; gape strongly curved, re- 

 stricted at corners of mouth by membrane between jaws (except in 

 Xenatherina) ; anus normal in position (except in Archomenidia) ; 

 belly short ; ventral fins more posterior in position, their insertions being 

 farther from the upper angle of the pectoral base than from the origin 

 of the anal fin, or about midway between these two points ; anal fin 

 usually elongate, with from 13 to 29 soft rays. Shores and streams of 

 ' the New World. 

 '. Premaxillaries fully protractile, the skin covering them separated by a 



deep fold from that of the forehead. 

 /\ Sides of head and all of trunk scaled. 

 «!. Jaws not produced into a beak ; premaxillaries very widely dilated 

 posteriorly ; origin of first dorsal behind that of anal only in large- 

 scaled genera, 

 f*. Jaws equal, oi' the lower included at its tip. 

 w^. Teeth well developed, in both jaws. 

 x^. Scales large, in 36 to 56 series ; pectorals reaching to or 

 beyond vertical from insertion of ventrals ; small fishes. 

 Tropical waters of the New World, ranging northward to 

 Nova Scotia and the Gulf of California, southward to 

 Rio de Janeiro and Ecuador. 

 y. Head not abruptly truncated posteriorly ; preopercular ridge 

 without a spine ; interorbital flat, or nearly so. 

 z^. First dorsal fin beginning before or over origin of anal 

 fin ; pectoral fin usually not falcate, and usually shorter 

 than the head ; belly rounded transversely ; body usually 

 with evenly curved contours ; rami of mandibles usually 

 much elevated posteriorly. 

 aa^. Scale margins strictly entire, or very slightly crenu- 

 late ; mandible little oblique, the head not being 

 notably angulated at its base ; mouth larger, the 

 maxillary reaching nearly to below front of eye, the 

 length of the mandible before corner of gape being 

 notably greater than that of the pupil ; jaws equal. 

 &&\ Anus normal in position ; air bladder not extended 

 backward over anal base ; gape less strongly arched ; 

 teeth of jaws in bands, those of the outer premaxil- 

 lary series not enlarged, directed downward. Nova 

 Scotia to Louisiana; Gulf of California. 



20. Menidia. 

 Anal fin short, with 15 to 19 soft rays. Coast and 

 coastwise streams of eastern United States. 



Subgenus Ischnomembras. 

 Anal fin longer, with 20 to 29 soft rays. Nova 

 Scotia to Louisiana; Gulf of California. 



Subgenus Menidia. 



