On Aquatic Carnivorous Coleoptera or DytLcidcB. 855 



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 coxse 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 iuterestinsr creature comes from South Africa. 



I. 25.— Genus A.SDEX. {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 coxse, so that these latter can be at 

 once observed to be contiguous : the inter-coxal process of the metasternum does not 

 project between the coxae, and is thus widely separated from attaining the mesosternal 

 fork. The front and middle legs are elongate, and the fourth joint of tlieir tarsi is 

 elongate and slender, the third joint being rather small and but little 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 Tjaidallhydrus of the Bidessini are the only 

 Dytiscidse 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. 



1. 26.— Genus HYDROPEPLUS. (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 coxse 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 ai-e longer than the tibise, and the tibial spurs are shorter than the first 



