On Aquatic Carnivorous Coleoptera or Dytiscide, 457 
This is a variable species in size and sculpture, and even in form : some individuals 
are quite dull, and others shining ; the more shining individuals are usually more 
convex and more distinctly, but not more closely punctured ; generally the elytra 
and thorax form an almost continuous outline, but in the more convex individuals 
this outline is a little more interrupted. The sexes are difficult to distinguish, but 
the basal joint of the front and middle tarsi is distinctly larger in the male. 
Hydroporus monticola, Sharp, was described from small, dull, and finely punctured 
individuals of this species. 
Northern Europe, and Arctic Siberia ; from 67° 20’ North (Sahlberg) to Geneva. 
556. Hydroporus cantabricus, n. sp.—Ovalis, latiusculus, fere sine pubescentia, 
sat nitidus, piceus, vel ferrugineus; antennis pedibusque rufis; prothorace disco 
sparsim subtiliter punctato, limbo distincte punctato; elytris crebre evidenter 
punctatis ; coxis posterioribus sparsim fortiter punctatis. Long. 33, lat. vix 2 m.m, 
This species comes very close indeed to some of the more shining varieties of 
Hydroporus melanarius, but I have not been able to connect it with them at present 
the elytra have the punctures more numerous, and their junction with the thorax 
forms a less indistinct angle, the colour, (especially of the head and thorax), is paler 
in all the specimens. 
Europe, (Reynosa). 395. 
557. Hydroporus insularis, n. sp.—Oblongo-ovalis, sat convexus, fere sine pubes- 
centia, piceus, prothorace lateribus late dilutioribus, antennis pedibusque rufis ; 
abdomine pectoreque nigris; prothorace medio sublevi, limbo minus punctato ; 
elytris sat crebre subtiliter punctatis ; coxis posterioribus sparsim fortiter punctatis. 
Long. 3%, lat. 2 m.m. 
Mas, pernitidus, tarsis anterioribus et intermediis articulo basali magno. 
Fem., oranino opaca, 
This species is much smaller than Hyphydrus memnonius, and is more finely 
punctured, in other respects it is extremely similar; of the few specimens I have 
seen all the females are opaque: the basal joint on the intermediate tarsus of the 
male is larger than in Hydroporus revelierei. 
Corsica. 393. 
558. Hyphydrus memnonius, Nicol., Hydroporus memnonius, M.C.—Oblongo- 
ovalis, minus convexus, fere sine pubescentia, piceus, prothorace lateribus late 
dilutioribus, antennis pedibusque rufis, illis sat elongatis, abdomine pectoreque 
nigris; prothorace antrorsum minus angustato, medio sparsim subtiliter, limbo 
