EEVISION OF AUSTEALIAN THEBAPONS.—OGILBY AND McCULLOCH. 101 



As is usual in freshwater fishes with a wide range, the Austrahan fiuviatile 

 Therapons exhibit considerable variation in both form and colour-marking, and it is 

 only by an examination of large series of specimens that we have been able to determine, 

 to our own satisfaction, the limits of the various species referred to in this paper. 

 The fin-fornnilae are generally constant, but in the widely distributed T. unicolor even 

 the number of dorsal spines varies from eleven to thirteen. The scale-counts, though 

 variable within certain limits, appear to afford useful characters for the discrimination 

 of species. Owing to the irregularity of the squama tion, however, the scales must be 

 counted in series, preferably upwards and backwards, and not individually. We 

 have found the number of scales between the lateral line and the middle of the spinous 

 dorsal fin (suj)ralateral scales), and excluding the dorsal sheath, to afford a ready guide 

 to some species. 



The freshwater Therapons range over the whole of AustraHa, and though most 

 abundant in the well-watered parts of Queensland, at least two species, T. unicolor 

 and T. percoides, extend into the small streams and waterholes of Central Australia. 

 Some are evidently capable of resisting long periods of drought by lying dormant in 

 the mud at the bottom of the pools in which they find themselves, until the advent 

 of rain, and consequent filhng of the pools with water, again vitaHses them into fresh 

 activities. They are a valuable item in the food supply of both aboriginals and 

 colonists, some species attaining considerable proportions. The marine species, 

 though edible, are but little valued as food. 



The species here dealt with may be distinguished by the following key : — 



a}. Lower opercular spine greatly developed, produced beyond the opercular lobe. Body with 

 longitudinal dark bands ; vertical fins with dark markings, spinous dorsal with a 

 large dark blotch. 

 b^. Scales larger, 7 i-8 supralateral scales .. .. .. .. .. .. .. theraps. 



b^. Scales smaller, 13-15 supralateral scales. 



c'. Body narrower, the depth slightly less than the length of the head ; longitudinal bands 

 almost straight . . . . . . . . . . . . . . . . puia. 



C-. Body deeper, the depth slightly g.eater than the length of the head ; longitudinal bands 

 strongly curved . . . . . . . . . . . . . . . . servus. 



<i-. Lower opercular spine smaller, not produced beyond the opercular lobe ; coloration various, 

 no large dark blotch on the spinous dorsal. 

 cP. Suprascapular bone not exposed, hidden by scales, 

 e^. Normally tliirteen dorsal spines. 



/^. 33-38 series of scales ; body with five narrow dark cross-bars. . .. .. percoides. 



p. 52-56 series of scales ; caudal fin with a broad oblique bat* on each lobe caudavittatus. 



e^. Nornaally twelve dorsal spines (rarely xiii or xi) ; coloration nearly uniform, or with small 



dark spots . . . . . . . . . . . . . . . . . , unicolor. 



d-. Suprascapular bone exposed, not hidden by scales, 

 r/^. Normally twelve dorsal spines. 



/i,^ Scales smaller, 75-90 between the origin of the lateral line and the hypnral joint. 



i^. Nostrils close together ; coloration nearly uniform .. .. .. .. bidyana. 



i^. Nostrils widely separate ; a dark shoulder-mark and dark cross bars on the body ; 

 fins spotted . . . . . . . . . . . . . . . . . . humeralis. 



Ir. Scales largi. r, less than 60 bctw-een the origin of the lateral line and the hypnral joint, 

 j^. Dorsal and anal spines very strong, longest dorsal spine longer than the rays, and 

 second anal spine much longer than the third. 

 h^. Nostrils close together : maxillary entirelj' covered by the lip . . . .interrvptua. 



k". Nostrils well separated : angle of the maxillary not covered by the lip . anienteus. 

 j^. Dorsal and anal spines weaker, the longest dorsal spine not longer than the rays, 

 second anal spine not or but little longer than the third. 



