On Aquatic Carnivorous Coleoptera or Dytiscide. 919 
which is not found in any of the other groups, viz., that the swimming feet in this 
sex are furnished beneath with swimming hairs along their outer edge, like the 
males, whereas in all the other groups only the males have the swimming tarsi 
ciliate in this manner. 
Species of this aggregate are found in most parts of the eastern hemisphere, and 
in North America, but are wanting in South America, one of the species, Dytiscus tri- 
punctatus has a very wide distribution from Japan, Australia, and New Caledonia, 
through the Philippine and Malay Islands and Asia, to Africa, and Southern 
Europe; and appears to be the most abundant species of the family Dytiscide. 
SECOND SYNTHESIS. (GaRIO RENTS) 
I]. 1.—Group Norerit. (Vide p. 263.) 
Three genera, one of which is an autogenus, while the other two contain each six 
species, form this secondary aggregate. The size of the individuals varies from 23 
to 5 mm. of length ; the form is very constant, transversely very convex above, 
almost flat beneath, the outline very continuous, forming an oval attenuate behind, 
there is no variegation of the upper surface, and the sculpture is peculiar, consisting 
of more or less isolated large punctures on the wing-cases (sometimes peculiarly 
asperate), and more or less completely wanting on the basal portion. The antenne are 
very variable, but sometimes show a most remarkable and extraordinary form in the 
males. The anterior tibiz bear a more or less elongate curved spur, and their 
outer angle is either conspicuously prominent (Pronoterus) or quite rounded off 
(Synchortus, Noterus.) The prosternal process is never large, sometimes very short 
and small, it is either rounded or obtusely acuminate behind. The suture between 
the hind coxa and metasternum approaches very near to the middle coxa; the 
hind coxal cavities are contiguous, and the swimming legs are either ideals or 
well developed ; the hind margin of their femur is destitute of any group of ciliz 
at its extremity, and the lower face of the femur is either impunctate (Pronoterus) 
or furnished with a transverse series of conspicuous punctures, extending somewhat 
parallel with, but at a distance from, the hind margin. 
The geographical distribution of the species of Noterini, is in accordance with 
their arrangement in genera, viz : tropical South America, one species (an autogenus) ; 
European region and Japan, six species (forming one genus) ; Madagascar and tropical 
Africa, six species (forming one genus). 
The South American insect is the lowest of the forms, and it is doubtful whether 
on the whole the European Noterus or the Africo-madagascarene Syrchortus is the 
higher form. It seems probable that the centre of distribution is either Madagascar 
or tropical Africa. 
