836 AUSTRALIAN COLEOPTERA, WITH DESCRIPTIONS OF NEW SPECIES, 



margins, the margin on either side of nearly even width and 

 scarcely narrower than half the width of the disc ; the middle of 

 the disc is occupied by a very strong dorsal channel, on either side 

 of which an equally strong impression runs from close to its base 

 obliquely forward to about the middle of the lateral ridge of the 

 disc ; there is also a strong foveiform impression on eitlier side 

 just within the anterior corner of the disc ; the surface of the 

 explanate margins is noticeably but less definedly uneven ; their 

 hinder third part (or rather more) is membranous ; their outline 

 (inclusive of that of the membrane) is gently and evenly convex ; 

 the anterior angles are well-marked, sharp, and minutely pointed 

 forward ; the hinder angles of the membrane are scarcely defined. 

 The surface of the elytra is not quite even and is marked with 

 well-defined coarsely punctate striae, which are scarcely enfeebled 

 behind ; the interstices are moderately convex and impunctate, the 

 apex of the elytra is moderately pointed. The underside is rather 

 shining, and I cannot find that it bears any distinct puncturation. 

 I do not observe any notable sexual difierences in the structure of 

 the ventral segments. 



No Australian species of this genus has been described hitherto, 

 so far as I know. Of European species 0. hicolon, Germ., is the 

 one that 0. Australis seems more particularly to resemble. Com- 

 pared with it (apart from the diff'erence in size), the maxillary 

 palpi of 0. Australis are much shorter and less stout, the in- 

 equalities on its head and prothorax are more sti'ongly defined, its 

 prothorax is not (or scarcely) punctulate, the sculpture of the 

 elytra continues, without becoming obsolete, to the apex. 



I have taken this little insect in the River Tod near Port 

 Lincoln and in the Torrens near Adelaide. 



Hydr^na Torrensi, sp.no v. 



Oblonga, postice minus dilatata ; supra obscure livida, capita 

 piceo ; clypeo subtiliter, capite postice prothoraceque sat fortiter, 

 punctulatis ; hoc transversim et longitudinaliter biimpresso ; 



