On Aquatic Carnworous Coleoptera or Dytiscide. S55 
with the metasternum is known only in it, in the South American Vatellini, and in 
the South African Andex. I have not been able to ascertain with certainty that the 
hind coxee are soldered to the ventral segments, but I believe this to be the case, 
and if so the genus may take its place in the Bidessini near Bidessus, though very 
distinct therefrom on account of the structure of the prothorax. 
This interesting creature comes from South Africa. 
I. 25.—Genus AVDEX. (Vide p. 371.) 
A single species is isolated under this name. It is but little known, and its 
individuals are of peculiar form, the prothorax being greatly narrower than the after- 
body, and almost narrower behind than in front; the most remarkable peculiarity 
of the species is however the fact that the prosternal process does not connect with the 
metasternum, but terminates in front of the middle coxe, so that these latter can be at 
once observed to be contiguous : the inter-coxal process of the metasternum does not 
project between the coxee,and is thus widely separated from attaining the mesosternal 
fork. The front and middle legs are elongate, and the fourth joint of their tarsi is 
elongate and slender, the third joint being rather small and but httle emarginate ; 
the swimming legs are rather slender and elongate. The head is rounded in front, 
but not margined. 
The Cape of Good Hope is the territory of this creature. 
The Vatellini, and the genus Tyndallhydrus of the Bidessini are the only 
Dytiscidee besides Andex that possess a prosternal process not reaching the 
metasternum. The Vatellini are exclusively South American insects, but 
Tyndallhydrus like Andex is a native of Southern Africa. 
I. 26.—Genus HY DROPEPLUS. (Vide p. 372.) 
This is another autogenus ; the individuals of this unique species have much the 
form and size of Hyphydri, but the surface both above and below is very densely 
and finely punctured. The front of the head is evenly rounded but without raised 
margin. The prosternal process is small, but somewhat elongate, it is very 
acuminate, its apex is somewhat bent downwards and rests against the short and 
inconspicuous inter-coxal process of the metasternum ; the extremity of this latter 
process is a little curved upwards to meet the prosternal process, but it does not 
connect with the mesosternal fork. The hind coxe are very largely developed, 
being very elongate with very arched anterior border, the wing of the metasternum 
deflexed outside this border forms a very slender parallel-sided band. The hind 
coxal cavities are quite exposed; the swimming legs are elongate and slender, 
their tarsi are longer than the tibie, and the tibial spurs are shorter than the first 
