Water Beetles of Japan. 67 
interstitils minus crebre punctulatis ; tibiis anticis integris. 
Long. IJ — \\ lin. 
This Insect is similar in form and colour to Mcgasternum 
boletophagum, but is greatly larger ; it is similar to that 
species in the structure of its under surface, but has the 
anterior tibia3 simple at the extremity ; as this character is 
only a sectional one in Cercyon, it cannot here be con- 
sidered of sufficient importance to justify the establishment 
of a new genus. 
The head and thorax are rather strongly and closely 
punctured, the latter with a row of larger punctures placed 
along the base. The elytra are moderately strongly punc- 
tate-striate, the instcrstices very finely pimctured. The 
under surface is coarsely and closely punctured. 
Two specimens without special locality. 
I' 2 
