On Aquatic Carnivorous Coleoptera or Dytiscide. 327 
195. Hydrovatus sumatrensis, n. sp.—Brevis, sat latus, nitidus, piceus subtus 
dilutior, antennis pedibusque testaceis, sat crebre minus fortiter punctatus ; antennis 
tenuibus simplicibus; coxis posterioribus fortiter sed minus crebre subinzequaliter 
punctatis. Long. 23, lat. 13, m.m. 
This species is not quite so closely punctured on the hind coxe as H. tusculus, 
and H. fasciatus, to which it is extremely closely allied, and it is also darker in 
colour. I detect no distinct sexual differences. 
Sumatra, (ten individuals sent by Wehncke). 447. 
196. Hydrovatus ovalis (Wehncke), n. sp.—Ovalis, brevis, sat latus, minus con- 
vexus, subnitidus, castaneo-ferrugineus, elytris basi sat crebre, subtiliter punctatis ; 
antennis sat crassis, coxis posterioribus dense fortiter punctatis. Long. vix. 2%, lat. 
lz mm. 
The antenne are rather stout, but are simple and not elongate. The surface of 
the thorax and elytra although little shining, is not evidently coriaceous; the 
punctuation of the thorax is very fine, and that of the elytra is also rather fine. 
Australia, (Brisbane). 1956. 
197. Hydrovatus sordidus, n. sp.—Brevis, latus, nitidus, sat convexus, postice 
acuminatus, testaceo-ferrugineus, elytris magis castaneis, confertim subtiliter 
punctatis ; antennis tenuibus, simplicibus. Long. 25, lat. 14 m.m. 
Very similar to Hydrovatus simplex (No. 183), hardly as large, slightly broader 
in proportion, rather less convex, with the punctuation of the upper surface finer, 
the antennze scarcely more slender and about the same length ; the front tibice are 
rather more slender than in H. cuspidatus (No. 180), and the punctuation of the 
under surface is less dense and distinct. Also very similar to Hydrovatus fusculus, 
but larger, broader, and less convex, the outline more acuminate and prolonged in 
its hinder part, the front legs rather broader, and the antenne a little longer. 
I have examined twelve individuals, but find no differences by which I can with 
certainty distinguish the sexes. 
Mesopotamia, Egypt, Arabia (El Hedjaz). 8. 
198. Hydrovatus humilis, n. sp.—Brevis, sat latus, convexus, vix nitidus, 
castaneus, elytris magis fuscis, sat crebre punctatis; antennis vix tenuibus ; coxis 
posterioribus crebre punctatis. Long. 23, lat. 1s m.m. 
Very similar to Hydrovatus simplex, (No. 183), but rather narrower, not so 
shining, and with the elytra not quite so coarsely punctured, and the front tibice 
rather more slender. . The only two individuals I have seen have the tarsi quite 
