608 On Aquatic Carnworous Coleoptera or Dytiscide. 
shorter than the inner one, and its extremity a little more slender and more 
curved. 
The two individuals before me are from different sources; one was recently 
collected by Mr. Blackburn, the other was formerly in Dejean’s collection; they 
differ in size and minor details, and may very probably prove to be two distinct 
species. 
Sandwich Islands. 869. 
921. Rhantus debilis, n. sp.—Ovalis, haud elongatus, depressus, nitidus, supra 
subtiliter reticulatus, nigricans, capite anterius et in vertice thoraceque rufescentibus, 
hoc disco infuscato, elytris nigro testaceoque vermiculatis ; prosterno anterius parum 
elevato, processu brevi, vix compresso, metasterni lateribus brevibus; tarsis 
posterioribus unguiculo externo quam interno fere duplo breviore. Long. 8, lat. 
vix 4 m.m. 
The male has the basal joints of the front and middle tarsi slightly incrassate, 
compressed, and furnished beneath with four rows of narrow palettes ; the claws of 
the front feet are rather short, strongly curved, the anterior one slightly longer 
than the other. 
Tahiti. 871. 
922. Rhantus annectens, n. sp.—Ovalis, haud elongatus, subdepressus, nitidus, 
subleevigatus, omnium subtilissime reticulatus, pectore abdomineque nigris, supra 
rufescens, capite in medio prothoracisque macula discoidali nigricantibus, elytris 
nigro testaceoque vermiculatis ; prosterno piceo, medio minus alte elevato, processu 
sat elongato, minus compresso. Long. 11, lat. 5 m.m. 
The male has the basal joints of the front and middle tarsi a little incrassate, 
and compressed, and furnished beneath with four rows of narrow palettes. 
I have seen only two very mutilated individuals; the species approximates to 
Colymbetes pulverosus, Steph., but is rather smaller, and the black marks on the 
elytra are larger, and form tortuous markings rather than spots: the prosternal 
process is a little shorter and less compressed, and the front border of the hind coxze 
approaches nearer to the middle coxe. 
Navigators Islands. 872. 
923. Rhantus plantaris, n. sp.—Ovalis, sat elongatus, angustulus, nitidus, sub- 
levigatus, subtilissime punctulatus, nullo modo reticulatus, testaceus, pectore, 
abdomine et capite utrinque ad oculos nigris, elytris nigro-irroratis, punctis seriatis 
conspicuis ; prosterno in medio minus elevato, processu sat elongato, parum com- 
