412 



II. Gillmembranes confluent, free from isthmus; gillopening 

 undivided. Gills on four arches, well developed. Teeth 

 in single series, which are only pluriserial near their 

 anterior end. 



1. Gillopening wide, extending up the sides to lateralline. Macrotrema p. 414. 



2. Gillopening narrow, restricted to ventral surface . . Synbranchus p. 415. 



i. Monopterus Lacepede. 

 (LACPDE, Hist. nat. Poissons II. 1798, p. 139). 



Body naked; elongate, cylindrical posteriorly compressed, 

 tail short, narrow, tapering into a point. Lateral line present. 

 Lips well developed, forming a rather broad fold, the lower 

 one reverted over the lower jaw. Posterior nostrils an oval 

 opening above anterior part of eye, anterior nostrils smaller 

 openings near end of snout in upper lip. Eye small, covered 

 by skin. Dorsal and anal low, rayless folds of the skin, con- 



a 



Fig. 210. Monopterus albus (Zuiew). X 2 /5- a anus : S gillopening. 



fluent with small caudal, which has a few rays. Pectorals and 

 ventrals absent. Teeth small, in bands on intermaxillaries, pala- 

 tines, pterygoids and mandibles. Gillmembranes confluent and 

 nearly entirely united with the isthmus; the gillopenings nearly 

 transverse ventral slits, only superficially confluent into a single 

 aperture. Four branchial arches, the three anterior with vestigial 

 gills ') and with three moderate slits between them. 

 Distribution: that of the single species. 



i) For the mode of respiration of this fish see VOLZ, Zool. Jahrb. Abt. 

 Anatomic XXIII. 1906, p. 163. 



