916 On Aquatic Carnivorous Coleoptera or Dytiscide. 
I. 76.—Genus SPENCHERHYDRUS. (Vide p. 701.) 
Three species form this ageregate; they are amongst the smallest of the 
Cybistrini, scarcely attaining 20 m.m. of length ; the yellow colour on the lateral 
part of the wing-case is extensive. The upper border of the hind coxz is greatly 
approximate to the middle coxal cavities, the laciniz of the metasternum being 
shorter and more linear, and less abruptly turned backwards than is the case in 
Cybister : the coxal lines are present; the prosternum is channelled along the 
middle ; the hind tarsi bear two claws of which the inner is much the larger, the 
unguicular cleft is broad and short, its anterior part curved, not angular : the 
palettes of the male tarsi are subelliptical, and without paper-like external prolon- 
gations. 
The three species agreeing in the above characters may be arranged in two 
groups according to whether the side of the thorax appears to be raised (S. 
pulchellus), or is normal and without any appearance of being margined (S. 
latecinctus, and 8. semiflavus). They depart from all the other Cybistrini by the 
male tarsi, the fifth joint of which is unusually elongate, while the palettes on the 
undersurface of the dilated basal joints are of peculiar form being destitute of the 
external paper-like prolongations found in all the other aggregates. ‘The genus 
agrees with Homceodytes in the structure of the hind claws, and the form of the 
unguicular cleft, but departs from it by the presence of coxal lines, as well as by 
the form of the lacinize of the metasternum, and the peculiar male tarsi. 
The three species are peculiar to Australia, and very rare in collections. 
I. 77.—Genus HOMGIODYTES. (Vide p. 703.) 
Three species form this aggregate. The individuals are of the usual Cybister 
form, with lateral stripe on the elytra. ‘he size varies from 15 to 27 m.m. of 
length. The coxal lines are completely absent, and by this character they depart 
from all the other Cybistrini; the structure of the hind claws and their point of 
insertion is much the same as in Spencerhydrus ; they differ therefore from 
Megadytes and Cybister in this respect, but the structures of the male tarsi and 
of the lacinize of the metasternum agree with the two genera just mentioned. 
The three species are sufficiently discrepant to form two well marked groups ; 
A, (Dytiscus atratus) size small (15 m.m. long) prosternal process distinctly chan- 
nelled along the middle ; postero-external angle of hind femora rectangular; 
intermediate male tarsi with largely developed sexual pubescence on the three 
basal joints, female without sexual sculpture ; and B, (C. scutellaris, and C. hookeri), 
size moderate (about 25 m.m. long), prosternal process with channel obsolete ; 
postero-external angle of hind femora acute or spinose ; male tarsi with sexual pubes- 
cence on the third joint but not on the two basal joints, female with very dense fine 
sexual sculpture on the wing-cases. 
The species are found in Australia and New Zealand, 
