136 



or small. Caudal forked, truncate or rounded.' Scales large or 

 moderate, rather deciduous. Lateral line running low down. 

 Gillopenings wide, gillmembranes not united with isthmus. 

 Third upper pharyngeals ankylosed, forming one large plate. 

 Distribution: All tropical seas, some species entering 

 fresh water or living exclusively in fresh or brackish water. 



Key to the indo-australian genera of 

 Hemirhamphidae. 



I. Dorsal beginning behind origin of anal and shorter 

 than that fin. 



1. Lower jaw produced into a beak Dermogenys p. 136. 



2. Lower jaw not produced into a beak Nomorhamphus p. 141. 



II. Dorsal beginning above or before origin of anal, 



generally longer than that fin. 



1. Lower jav/ produced into a beak. 



a. Part of lower jaw beyond extremity of upper 



jaw provided with teeth. Size small Hemirhamphodon p. 142. 



b. No teeth on part of lower jaw beyond extre- 

 mity of upper jaw. 



x. Caudal forked. No modified anal rays in 



the male Hemirhamphus p. 145. 



/3. Caudal truncate or rounded. Anal rays more 



or less modified in males Zenarchopterus p. 162. 



2. Lower jaw not produced into a beak Arrhamphus p. 171. 



i. Dermogenys van Hasselt. 



(VAN HASSELT, Algem. Konst- en Letterbode I. 1823, p. 131). 



Elongate, rather compressed. Mandibles prolonged into a 



beak, which has no teeth except in the part opposite to the 



intermaxillaries. This beak is bordered along each side by a 



fold of the skin, which stands out horizontally but is not 



Fig. 52. Dermogenys orient alls (M. Web.). X l3 /4- 



always visible in preserved specimens. Intermaxillaries forming 

 a tapering plate, which is truncate in front and therefore 

 has the shape of a trapezium. Small, pointed teeth in both 

 jaws. Dorsal shorter than anal and beginning behind that fin. 



