On Aquatic Carnivorous Coleoptera or DytiscidcB. 345 



Group 3. — Short broad species without pubescence, but with a tuost remarkably- 

 sculptured surface, the punctures on the under surface being especially 

 large, the plica at the base of the thorax is continued on to the 

 elytra in so conspicuous a manner that it forms a sort of elongate- 

 carina extending half the length of the wing cases. Species 247 to 

 254. 



Group 4. — Hind coxae not longer than broad ; surface not entirely glabrous, 

 plica OQ elytra not extending one-half of length of the wing cases ; 

 under surface with an extensive development of moderately coarse 

 punctuation. Species 255 to 268. 

 N.B. — The species placed at the end of this group connect it with 

 the following one. 



Group 5. — Hind coxpe longer than broad, under surface with but little coarse 

 punctuation, apex of elytra but little acuminate ; elytra with a basal 

 plica, which is continued (except in two species, Nos. 291 and 292), 

 on to the base of the elytra either as a short punctiform impression 

 or as a distinct line. Species 269 to 325. 

 This group is further sectionized thus : — 



A. Each wing case provided with a distinct sutural stria. Species 269 



to 292. 



B. Wing cases destitute of a distinct sutural stria. Species 293 to 325. 



Group 1. 



242, Hydroporus cribrosus, Schaum, M.C. — Ovalis, brevis, latus, convexus, elytris 

 creberrime fortiter punctatis, vix nitidis ; pectore crebre sequaliter fortiter punc- 

 tato. Long. 23^, lat. ih m.m. 



Egypt, (Cairo). 98. 



243. Bidessus migrator, n. sp. — Ovalis, brevis, latus, convexus, elytris crebre 

 fortiter punctatis, subnitidis ; pectoris lateribus fortiter, medio obsolete, punctatis. 



Long. 2, lat. It m.m. 



Very closely allied to Hydroporus cribrosus, Schaum, but rather narrower, and 

 with the punctures on the elytra not quite so close, and slightly coarser : the punc- 

 tures on the hind coxae are finer, and those on the middle of the sternum much 

 finer than in the Egyptian species. 



Australia, (Rockhamptou). 9P. 



