water-beetles of Japan. 457 



longitudinal impression on each side of the middle channel is seen 

 to be divided into two impressions ; the large impression marking 

 off the portion at the anterior angles is deep and very broad. The 

 under surface is rendered ashy by a very minute dense pubescence, 

 the two terminal segments being left bare. 



The species is not closely allied to any other, but may 

 be placed near 0. nanus, St. 



A single example was met with at Miyanoshita in 

 May, 1880. 



Hydrochus cequalis. 



Supra, metallico-ferrugineus, subtus niger, autennis, palpis pedi- 

 busque testaceis ; prothorace fortiter punctato, subinaequali, vix 

 foveolato, posterius angustato ; elytris seriatim fortiter et profunde 

 punctatis, interstitiis angustis, fere omnino similibus et sequalibus. 

 Long. 3 mm. 



This little insect, though very similar to H. japonicus, 

 is distinct by the absence of evident areolae on the 

 thorax. 



Only two individuals have been found, one at the 

 Ogura Lake, the other at Osaka, both in the early days 

 of July, 1881. 



Helophorus sp. ? 



The only evidence of the occurrence of any species of 

 this well-known genus in Japan* is a very dirty speci- 

 men, found at Kobe, of what may perhaps be our common 

 species, H. griseus, though its condition does not allow 

 this to be certainly decided. 



Cyclonotum orhiculare. 

 Hydrophilus orhicidaris, Fab., Syst. Ent., 229, 5. 



The Japanese individuals are rather less globose, and 

 have a slightly coarser punctuation, than the European 

 individuals. 



It is apparently confined to the north in Japan, having 

 been found at Hakodate, SaiDporo, and Otaru, in the 

 island of Yezo. 



Mr. Lewis failed to take Sphceridium in Japan, al- 

 though continually looking for it. The genus is as 

 common in China as in Britain. 



* Since this was written a second species of Helophorus has been 

 received, and is described at the end of this paper. 



