On Aquatic Carnivorous Coleoptera or Dytiscidce. 833 



structures of the two, just in that proportion has the theory of genetic relationship 

 between them become incredible. Now as Pelobius stands in relation to Carabidse 

 and Dytiscidas as Archseopteryx does (or did) to birds and lizards, it is quite 

 clear that most interesting fossil does not any more prove that birds are descended 

 from lizards, than Pelobius proves that Dytiscidee are descended from Carabidse, 

 or Carabidse from Dytiscidae. 



I. 2.— Genus NOTOMICRUS. {Vide p. 260.) 



The four species forming this aggregate, are the most minute of the Dytiscidae 

 and among the smallest Coleoptera, the length attained being only about 1 m.m. 

 The form is rather depressed, the surface extremely polished and shining, without 

 punctuation or pubescence. The antennse have no thickening of the middle joints, 

 and are short and simple. The anterior coxaj are minute and placed at a considerable 

 distance from the front of the thorax ; the prosternal process is quite small and is 

 rounded behind. The anterior tibice and tarsi are sinq^le, the former with scarcely 

 developed spur, the latter with the basal joint not notably elongate. The breast 

 is excessively polished so that no trace of the suture between the hind coxa and 

 metasternum can be detected. The coxal processes are slightly prolonged towards 

 their outer hinder angle, the coxal cavities are slightly separated, with the coxal 

 notch very minute and narrow. The swimming legs are excessively feeble, and the 

 hind tarsi are very slender, longer than the tibiee. 



The genus is readily distinguished by the simple anterior legs, by the obliterated 

 suture between the coxa and metasternum, and by the very feeble swimming 

 legs. I have not been] able to see the palpi, nor to ascertain well the details oJ' 

 the structure of the tarsi. 



As it stands at present the genus is divided between Australia and South 

 America ; but possibly one of the two species from the latter locality may be found to 

 be sufficiently difierent from the others to justify a new generic name being formed 

 for it ; it has the swimming legs much less elongate and slender ; other species will 

 no doubt be discovered, and this may admit of the characters being correctly formu- 

 lated. At present I cannot pronounce an opinion on the relations of this genus to the 

 other genera of Noterini and I shall therefore leave it isolated in the second 

 synthesis ; I think it probable that this course will prove to be the natural one, 

 even after the structure has been more completely ascertained, for I very much 

 doubt whether it has any close approximation to Hydrocoptus, or any other form 

 yet brought to light. 



