604 On Aquatic Carnivorous Coleoptera or Dytiscide. 
reticulatis, punctis seriatis conspicuis, ad apicem oblique truncatis, angulo externo 
nullo. Long. 10%, lat. 54 m.m. 
The male has the basal joints of the front tarsi a good deal incrassate and com- 
pressed, and furnished beneath with long hairs and with palettes, their claws are 
elongate, sinuate, and unequal, the posterior being incrassate, and a little longer 
than the front one, this latter being only moderately slender ; the middle tarsi have 
the basal jomts incrassate and greatly compressed, and clothed beneath in a manner 
similar to the front ones ; the apical ventral plate is sinuate on each side, so as 
to appear produced in the middle, and this central part bears long deep ruge. In 
the female this segment is but little sinuate at the sides, and the hinder part is 
marked with moderately short rugze ; in this sex the elytra have on their basal 
portion some short irregular scratches, which appear to vary in their number and 
extent in different individuals. 
Chili. 866. 
916. Colymbetes preemorsus, Er., Rhantus varius, M.C_—Ovalis, sat elongatus, 
angustulus, rufo-testaceus, pectore, (maris sednon feminze abdomine) verticeque 
nigris, elytris nigro-reticulatis, ad apicem truncatis, angulo externo rotundato ; 
prosterno in medio crasse compresso-elevato. Long. 9, lat. 44 m.m. 
The male has the basal joints of the front tarsi much incrassate and compressed, 
and furnished beneath with long hairs and with large palettes ; their claws are very 
unequal the front one being slender, moderately long, nearly straight, and very 
acuminate, while the hinder one is a good deal longer and is thickened, sinuate and 
acuminate, and has a projecting tooth close to the articulation; the middle tarsi 
have their basal joints much incrassate and compressed, and clothed beneath in a 
similar manner to the front feet, their terminal joint is elongate, and bears long, 
slender, nearly equal claws ; the apical ventral segment in each sex is deeply sinuate 
on each side, and in the male is longitudinally strigose, but in a variable manner. 
The female has numerous very short scratches on the elytra, and the serial punctures 
are less distinct than in the male. 
The species is somewhat variable in colour ; besides the sexual disparity in the 
colour of the ventral segments, there is also a variation independent of sex, the 
breast being sometimes but little black, and occasionally in the male the black 
colour does not entirely cover the ventral segments, while on the other hand in 
certain females, the black colour is not entirely wanting; the prothorax is some- 
times blackish at the base, and occasionally has traces of two black spots on the 
disc. ‘The size and the thickness of the hinder of the two front claws of the male 
also vary somewhat. 
South America, (Chili, Bolivia, Monte Video). 867. 
