water-beetles of Japan. 445 



legs are slender, the femoral setse very small. The front 

 and middle tarsi of the male are almost undilated, but 

 are furnished beneath with very evident glandular pube- 

 scence. 



A single example of the male sex was found in Higo 

 in 1882. 



Agahus optatus. 

 Ovalis, parum convexus, niger, nitidus, antennis, palpis tarsisqne 

 rufis, pedibus piceis, elytris versus latera giittula parva pallida ; 

 corpore supra densissime omnium subtilissime reticulato. Long. 

 6^ mm., lat. d^ mm. 



Notwithstanding the fact that the coxal lines are less 

 directed outwards behind than usual this species may 

 be placed in the same group b,s A. jajjonicus, from which 

 species it is readily distinguished by its smaller size 

 and the uniform black colour ; the prosternal process is 

 only moderately broad, but is flat and distinctly mar- 

 gined ; the swimming-legs are slender, their tibite glabrous 

 on the infero-external face ; the hind coxae are rather 

 large, the wing of the metastermum moderate. 



A single female example was found in Kiishiu in 1874 

 {Mr. Wada). 



Platamhus fimhriatus. 



Ovalis, angustulus, convexus, nitidus, rufus, abdomine apicem 

 versus picescente, supra subaenescens, capitis maculis magnis, pro- 

 thoracis lateribus, elytrorumque marginibus laterali basalique late 

 flavis ; elytris politis, punctis seriatis magnis impressis. Long. 

 7 mm., lat. 3^ mm. 



This insect is narrower than Dytiscus maculatus, and 

 readily distinguished by the very broad lateral and basal 

 margins of the upper surface, and by the very large im- 

 pressed punctures on the elytra. 



The series of nine examples shows very little variation, 

 and the male characters are very slight, there being 

 only an extremely slight incrassation of the front and 

 middle tarsi. 



Found at Chiuzenji in the fourth week of August, and 

 in the lake at Hakone. 



Copelatus japonicus. 

 Oblongo-ovalis, depressus, fusco-piceus, capitis prothoracisque 

 marginibus dilutioribus, elytrorum marginibus laterali basalique, 



