On Aquatic Carnivorous Coleoptera or Dytiscidce. 607 



resembles the male in sculpture : it has no cilias on the outer edge of the hind tarsi 

 beneath, whereas in the male, both sides of the tarsi are ciliate. 



North America, (Hudson's Bay). 11G5. 



I. 62.— Genus RHANTUS. 



Side piece of fourth and following ventral segments very narrow ; metasternal 

 groove distinct and well defined ; terminal joint of hind tarsus not longer, (or but 

 little longer) than the preceding one; thorax nearly always margined; colour of 

 "wing-cases frequently yellow speckled with black. 



This genus as known to me comprises about forty species* ; there are but few 

 parts of the world where it is not represented by one or more species. They are 

 difficult to determine, and I cannot at present arrange them in natural groups that 

 would make the task more easy. 



920. Colymbetes paeificus, Boisd., M.C. — OvaUs, minus convexus et elongatus, 

 nigricans, vix nitidus, sublcevigatus, subtilissime punctulatus, nullo modo reticula- 

 tus, nigricans, vertice rufo-bimaculato, prothoraeis lateribus rufis, elytris nigro 

 rufoque vermiculatis, punctis seriatis magnis; antennis pedibusque rufis, pedibus 

 posterioribus picescentibus; prosterno in medio minus incrassato, processu brevi, sat 

 compresso; unguiculis posterioribus longitudine parum dissimilibus. Long. 9f, lat. 

 5 m.m. 



The male characters are very slight, the basal joints of the front and middle 

 tarsi being a little incrassate, and furnished beneath with four series of extremely 

 rudimentary palettes. The claws are rather short, simple, and equal. 



This very interesting species has the outei- claw of the hind foot just visibly 



* The following uames should probably also be assigned to the genus : — Colymbetes assimilis, Kirb, 

 (No. 1,213); North America. — Colymbetes darwinii, Bab. (No. 1,219), near No. 926; Patagonia. — 

 Coljanbetes discicollis, Aube (No. l,221)? = No. 924; Java. — Colymbetes di.stigma, BruUe (No. 1,223), 

 gen. dub. ; South America. — Colymbetes dujjonti, Aube (No. 1,225), near No. 92G; South America. — 

 Colymbetes fonticola, Phil. (No. 1,226); near No. 926 ; Chili.— Colymbetes gutticollis. Say. (No. 1,230) 

 ?No. 935 Var. ; Mexico. — Colymbetes interclusus, Walk. (No. 1,234-) ; Ceylon. — Colymbetes marmoratus, 

 Perroud, (No. 1,239), gen. dub.; New Caledonia. — Colymbetes obsciu-icollis, Aubii (No. 1,241^ 

 ?nearNo. 926; Chill — Colymbetes socialis, Wat. (No. 1,250) ; Rodriguez Island. — Colymbetes suturalis, 

 Macl. (No. l,254)'?=No. 1,221; Java.— Colymbetes vibicicollis, Hoch. (No. 1,257) '«=No.924; Caucasus.— 

 Hydaticus riehli, Wehncke (No. 1,320) ; Cuba. — Rhantus (?) consimilis, Motsch. (No. 1,500) 1 near No. 

 944 ; California. — Rhantus flavo-griseus. Crotch (No. 1,501) near No. 935 ; North America. — Rhantus 

 luteicollis, Gebl. (No. 1,502), near No. 951 ; Siberia. — Rhantus nigriventris, Motsch. (No. 1,503), near 

 No. 924 ; Kamtschatka. — Rhantus nigropunctatus, Motsch. (No. 1,504 ; near No. 954) ; Songoria. 



