On Aquatic Carnivorous Coleoptera or Dytiscide. 275 
52. Hydrocanthus semperi, Wehncke, Berl. Zeit. 1876, p. 223.—Ovalis, sat 
convexus, posterius attenuatus, pernitidus, niger, capite prothoraceque ad angulos 
anteriores rufo-testaceis, illo posterius infuscato ; antennis testaceis, pedibus obscure 
rufis, Long. 23 m.m., lat. 13 m.m. 
This is a small and rather short species, distinguished from H. luctuosus (No. 60) 
and allies by the unspotted elytra. 
Philippine islands; Luzon. 614. 
53. Canthydrus arabicus, n. sp.—Breviter ovalis, convexus, posterius attenuatus, 
pernitidus, piceus, capite prothoraceque lateribus testaceis; elytris guttula parva 
pone medium testacea, omnino levigatis; antennis testaceis, pedibus rufis. Long. 
32, lat. 1? m.m. 
This species is very closely allied to Hydrocanthus guttula (No. 54), but is rather 
smaller, and besides the colour differences, is remarkable for being without any 
punctures on the wing-cases. Immature individuals are entirely yellow. 
Arabia, (Hedjaz, Millingen). 1147. 
54. Hydrocanthus guttula, Aubé, M.C.—Ovalis, convexus, posterius attenuatus, 
pernitidus, niger, capite anterius, thoraceque ad angulos anteriores rufo-testaceis ; 
elytris guttula parva pone medium testacea, punctis sparsis sat conspicuis ; antennis 
testaceis ; pedibus rufis, posterioribus magis obscuris. Long. 3, lat. 1f m.m. 
This species is broader and more convex than Hydrocanthus notula (No. 55), 
and has the yellow colour at the anterior angle of the thorax much less extended ; 
the punctures on the elytra are more conspicuous. 
Madagascar ; Mauritius. 490. 
55. Hydrocanthus notula, Er. M.C.—Ovalis, sat convexus, posterius attenuatus, 
pernitidus, niger, capite anterius, prothoracisque lateribus rufo-testaceis, elytris 
suttula parva pone medium testacea ; antennis testaceis, pedibus rufis, posterioribus 
magis obscuris. Long. 35, lat. 1§ m.m. 
The red colour on the head and thorax, is more extended in the male than in the 
female ; there is sometimes a minute yellow dash at the base of the elytra close to 
the outer margin. 
Egypt ; Tangier ; (Angola fide Erichson). 489. 
56. Canthydrus ornatus, n. sp.—Ovalis, sat convexus, posterius attenuatus, 
pernitidus, niger, capite, prothoracis lateribus, elytrorum macula humerali aliaque 
TRANS. ROY. DUB. SOC., N.S. VOL. ITI, 20 
