282 On Aquatic Carnivorous Cnleoptera or Di/tisculce. 



81. Noterus grandis, Lap. Hydrocanthus grandis,M.C. — Minus latus, convexus, 

 pernitidus, piceus, capite thoraceque quam elytris dilutioribus, antennis rufis ; elytris 

 pone humeros sinuatis, sublEevigatis ; spatio inter coxas anteriores minus lato, 

 subelevato ; prosterno medio, pectoris coxarumque parte elevata crebre punctatis. 

 Long. 7, lat. Zh m.m. 



In the male the apical ventral segment is very little if at all compressed towards 

 the apex. 



Africa, (Senegal, Gaboon). 473. 



82. Hydrocanthus deyrollei, n. sp. — Crassus, robustus, latiusculus, sat nitidus, 

 niger, antennis rufis,pedibus piceis, elytris seriebus duabus punctorum sat distinctis,et 

 versus latera punctis sparsis, lateribus pone humeros, vix sinuatis ; coxis anterioribus 

 late separatis ; prosterno, pectore medio laminisque coxarum impunctatis. Long. 

 8 m.m. (vix), lat. il m.m. 



The male has the hinder part of the apical ventral segment much compressed so 

 as to form a ridge terminating in a point. 



Africa, (Gaboon, Brussels Museum ; found I believe by H. Deyrolle). 472. 



II. 4. — Group Vatellixi. 



Prosternal process not reaching the metasternum, but terminating in front of and 

 between the middle coxeb; front andmiddle tarsi four jointed, frequently very elongate ; 

 outline of body discontinuous at junction of thorax and elytra. S^Yimraing legs slender. 



This group represents in the Dytisci Fragmentati series the Hydroporides of the 

 second series. The three genera are South American, and very rare in collections, 

 except Derovatellus. 



Ventral sutures very deep, YATELLUS,{mde\>.2ib) 



Ventral sutures normal, 



Mesostemum very largely visible ; \ MAOROVATELLUS, 

 size moderate (G-8 m.m. long), j (vide below). 



Mesostemum but little yhMe;} DEROVATELLUS, 

 .size small (4 m.m. long). J (yide p. 286). 



L II.— Genvis MACROVATELLUS. 

 Mesostemum largely exposed between the prothorax and metasternum. Outline 

 of thorax and elytra very discontinuous. 



The Macro vatelli are moderately large insects (6 — 8 m.m. long). 



The species* are very similar to one another and extremely rare in collections. 



♦Vatellus grandis, Buq. (No. 1,511, luij. op.), from Cayenne is probably another species of the genus. 



