On Aquatic Carnivorous Coleoptera or Dytiscide. 317 
I. 15.—Genus NEPTOSTERNUS. 
Prosternal process tridentate; spurs of hind tibiew acuminate at apex. Head 
rather short ; hind angles of prothorax very acute. 
The unique species inhabits Madagascar and East Africa. 
175. Neptosternus ornatus, n. sp.—Oblongo-ovalis, sat latus, subdepressus, 
nitidus, levigatus, rufus, elytris fuscis, maculis decem rufis; prothorace angulis 
posterioribus retrorsum spectantibus, per-acutis. Long. 33, lat. 2 m.m. 
The peculiar hind angles of the thorax of this species will prevent its being 
confounded with any other known to me. I have examined about twelve indi- 
viduals, in all of which the front tarsi are slender, and I do not see any sexual 
distinction. 
Madagascar: Zanzibar. 594. 
IV. 2.—Srrizs Dytisci Complicati. 
Dytisciaze having the metathoracic episternum extending so far towards the 
middle of the body as to reach the middle coxal cavity ; internal laminz of hind 
coxe closely coadapted by a straight suture. 
The members of this extensive and complex series may be thus tabulated :— 
Hind coxe separated from metasternum by a directly} 
transverse suture; mentum reaching as far forward > Ala PHI A os 
as front of the labrum. ( Vide p. ») 
Im all the following aggregates the hind coxe are separated from metasternum by a suture directed 
forwards as it proceeds outwards, and the mentum does not extend so far forward as the labrum :— 
{ Prosternal process | 
much deflected 
from direction 2 SG | 
of prosternum. + sss ae HYDROPORIDES., 
Prosternum  de- 
flected between 
the front coxze 
so that the pro- | Front tarsi (Viderp. 319.) 
sternal process usually with 
is placed on a only 4 joints. j 
quite different 
plane of direc-1 Prosternal process! 
. tion from that but little de- 
of the proster- flected el 
num ; this not | lane of direc- Ti Ke 
incrassate along | ‘fom of pro-? = = JUTE a AIDES ; 
middle; front| sternum ; front | (ide ps489)) 
tarsi usually 4- tarsi 5-jointed, 
jointed. | scutellum not 
{ visible. J 
