On Aquatic Carnivorous Coleoptera or Dytiscidea. 835 
thought it justifiable under these circumstances to use the name for the aggregate 
in which the species just referred are included, but as Motschoulsky never attempted 
any definition of Hydrocoptus, and included under it both Hydroporides and 
Noterides, his name had better not be cited in connection with it. 
I. 4.Genus PRONOTERUS. (Vide p. 263.) 
The unique species is of small size ; its individuals only attain 2 m.m. of length, 
and their appearance is that of a small parallel Noterus. The anterior tibiz are 
short and broad, and their outer angle is distinctly spinose ; at the inner angle 
they have a minute spur, and a second more elongate one, this latter is curved : 
the basal joint of the front tarsus is a good deal incrassate, and elongate. The 
last joint of the labial palpus is dilated ; the prosternum is straight from the front 
margin to the end of the prosternal process; this is of moderate size, with its ter- 
minal angles rounded, but is truncate at the extremity: the interior lamine of the 
hind coxee approach very close to the middle coxze, and the wings of the metasternum 
are quite small; the suture separating them from the hind coxe is quite distinct. 
The coxal processes are almost truncate, their outer angle being scarcely at all pro- 
duced ; the coxal cavities are almost contiguous, and no evidence of their not being 
absolutely so can be seen without dissection. ‘The swimming legs are moderately 
well developed, the tibie being very distinctly flattened and incrassate, so as to be 
much broader than the tarsi, these latter are a little longer than the tibie, their 
basal joint elongate, considerably longer than the three following ones together ; 
the two claws are short, and rather stout, equal, curved. 
This is an interesting form, apparently intermediate between Hydrocoptus and 
Noterus: it has quite the appearance of the Hydrocopti. 
I. 5.—Genus SYNCHORTUS, (Vide p. 264.) 
This aggregate consists of six species, whose individuals have the appearance of 
small Noteri, but when a punctuation is present on the wing-cases it is of a very 
peculiar kind, and gives rise to an appearance of asperities, rather than of round 
depressions. The antennze are slender with the terminal joints more elongate than 
the basal ones. The anterior tibize are rather slender, with the outer margin 
densely set with very short thick cilize, the outer apical angle has almost disappeared, 
the inner one is furnished with a slender elongate curved spur, or hook : the basal 
joint of the front tarsus is very largely developed. The prosternal process is short, 
broad, very rounded behind, and is as it were continued forwards between the coxee 
to near the front margin of the thorax, and becomes quite gradually and gently 
obsolete there. The suture between the hind coxa and metasternum nearly touches 
the middle coxa ; the coxal processes are much developed, and produced at their 
outer angles ; the hind coxal cavities are contiguous; the swimming legs are 
TRANS. ROY. DUB. SOC., N,S., VOL. U. 5 P 
