On Aquatic Carnivorous Coleoptera or Dytiscide. 389 
II. 9.—Group Hyproporii. 
Front and middle tarsi 4jointed (with a small additional joint occasionally 
visible at the base of the terminal joint) ; mesosternum but little visible, being 
placed at such an angle with the metasternum that it is much concealed between 
this and the prothorax: hind coxal cavities nearly or quite contiguous; ventral 
segments not soldered to cox ; prosternal process acuminate behind. 
There are ten genera comprised in the Hydroporini. 
I find it difficult to make 
a dichotomous key that would be practically useful for their identification, and 
have therefore drawn up the following series of abbreviated characters ; these can 
be glanced through in a few minutes and the genus in this manner ascertained with 
certainty. 
Elytral ligula free and abrupt, terminal joint of front tarsus very short in 
comparison with the third joint. Three species from the eastern 
portion of the Mediterranean region. J 
Elytral ligula free, abrupt, terminal joint of front tarsus not very short in ] 
comparison with the third joint, although often much concealed by i 
the deep fissure of the latter. Numerous species in the European and | 
North American regions. J 
Elytral ligula abrupt on the posterior face, gradually raised in front ; hind ] 
coxal cavities approximate; posterior portion of epipleure very 
narrow ; humeral area of epipleura limited behind by a well-marked 
raised line. Six species, extending from Madagascar to Southern 
Europe. J 
Elytral ridge very little developed ; posterior coxal cavities much exposed 
and a good deal separated ; posterior portion of epipleura very narrow ; 
hind tibia with only the serial punctures on the infero-external face. 
Three species peculiar to Australia. 
Elytral ligula absent ; posterior portion of epipleura comparatively broad ; 
hind tibia with only the serial punctures on the infero-external face ; 
posterior femora slender, with rounded outer angle. Four species 
found in Australia and Tasmania. 
on the infero-external aspect; the true fourth joint of front tarsus 
searcely visible. Eight species found in Australia and New Zealand. 
] 
| 
j 
] 
J 
Posterior portion of epipleura comparatively broad; hind tibia punctured \ 
True fourth joint of front tarsus quite conspicuous, distinctly disengaged }] 
from the lobes of the third joint : (this structure more exaggerated in N 
the males than in the females). Eight species found in Australia and | 
Tasmania. J 
Hind tibia only with serial punctures on the infero-external aspect. } 
Terminal portion of epipleura rather broad: posterior femora stout ; 
their postero-external angle sharply defined. Six species found in 
Australia and Tasmania. 
HY PHOPORUS. 
(Vide p. 390.) 
C@LAMBUS. 
(Vide p. 394.) 
HEROPHYDRUS. 
(Vide p. 392.) 
PAROSTER. 
(Vide p. 391.) 
CHOSTONECTES. 
(Vide p. 408.) 
ANTIPORUS. 
(Vide p. 410.) 
NECTEROSOMA. 
(Vide p. 412.) 
MACROPORUS. 
(Vide p. 416.) 
3 E 2 
