BEETLES. 37 



* H. aquaiicus, Linn. (Plate IV., Fig. 20). Wing-cases deeply i|| 

 punctate-striate, dark brownish-yellow, with a metallic shine. 



It varies considerably in size. It is widely distributed. 



* H. granularis, Linn., is only 2 mm. in length, brownish- 

 yellow, with indistinct black spots, and a small distinct dark 

 spot beyond the middle of the suture. It is rare. 



OCHTHEBIUS, Leach. 

 Thorax narrowed behind. Antennae with a club composed 

 of five joints. The first joint of the labial palpi is very short, 

 and the two next are of equal length. They live on the 

 margins of standing water and brooks, under stones and 

 macerated twicjs. 



* 0' 2njgmceus, Fabr. Only 1 J mm. long, oval, slightly convex, 

 pale pitch-brown. The whole of the thorax and abdomen 

 is uniformly punctate -striate. It is a common species. 



Genus Hydr^na, Kugel. 

 Quite small species of an elongated form, with an octagonal 

 thorax, having a curved excavation on each side. The wing- 

 cases are longer than broad. They are found under water- 

 plants and under stones. 



* H. gracilis, Germ. Black and somewhat convex, with the 

 antennae, legs and palpi light red. The wing-cases are dark 

 reddish-brown, scarcely broader than the thorax, each with six 

 rows of deep punctures, not closely placed. Length, 1-2 mm. 



Genus Cyclonotum, Erichs. 

 Body hemispherical. Wing-cases separately rounded behind. 

 The metasternum is keeled and projects between the middle 

 coxce. They are found in stagnant water. 



* C. orbiculare, Fabr. Shining black, densely punctate. 



