On Aquatic Carnivorous Coleoptera or Dytiscidce. 269 



This group comprises only two genera ; both have a very wide geographical 

 distribution. 



Prosternal process very broad behind ; bind tibife very broad ; ) EYDROCANTHUS, 

 size 4-7 m.m. of length. | {mde p. 279.) 



Prosternal process moderately broad behind; hind tiljire raihev \CANTHYDRUS, 

 slender ; size less than 4 m.m. of length. j (vide below). 



I. 9.— Genus CANTHYDRUS. 



Prosternal pi'ocess only moderately broad, not broader than long ; swimming 

 legs rather slender. 



The numerous species* inhabit the warmer parts of the Old and New Worlds ; 

 they are but little understood as yet, and very similar to one another. 



30. Canthydrus sculpturatus, n. sp. — Ovalis, sat convexus, nitidus, ferruginous, 

 elytris abdomineque fuscis ; illis crebre profunde arguteque punctatis, punctis 

 elongatis, versus apicem densioribus. Long, 2|, lat. If m.m. 



The punctuation of the elytra makes this a very easily distinguished species. 

 The only individual I have -seen is a female, and has the apical ventral segment 

 almost without impression. 



Brazil, (Santa Rita, August, 1850, Dr. Sahlberg). 515. 



31. Canthydrus vicinus, n. sp. — Ovalis, sat convexus, nitidus, ferrugineus, elytris 

 sat crebre punctatis; prosterni jirocessu parce punctate. Long. 2f, lat. If m.m. 



Extremely similar to Canthydrus sculpturatus but not so broad, and with 

 prosternal jsrocess and coxal laminaa more sparingly punctured. The two individuals 

 before me are male and female. The male has a small indistinct oblonar flattening 

 or depression at the base of the apical ventral segment in the middle ; in the female 

 there is a very obscure indication of carination along the middle of the hinder part 

 of this segment. The male specimen has the elytra more closely and coarsely 

 punctured than in the female, but I do not know whether this is sexual or merely 

 an individual variation. 



Brazil, (Santa Rita, August, 1850, Sahlberg). 514. 



* In addition to those enumerated in the text, the following species should probably be placed in 

 Canthydrus. Hydrocanthus auritus Regt. (No. 1,324 huj. op.) ; Manilla. — Hydrocanthus lineatus, 

 Wehncke (No. 1,326), near No. 49; Mexico. — Hydrocanthus rubripes. Boh. (No. 1,328), 1 near No. 45; 

 Uruguay. — Hydrocanthus testaceus, Boh. (No. 1,330), near No. 70; China. — Suphis puncticoUis, Crotch, 

 (No. 1,506), near No. 48; North America. — Supliis semiiaunctatus, Lee. (No. 1,507); North America. — 

 Whether Hydrocanthus nanulus, Lee. (No. 1,327, North America) belong to the genus, is somewhat 

 doubtful. ■ - 



2 N 2 



