692 On Aquatic Carnivorous Coleoptera or Dytiscidce. 



specimens from trojiical Africa, show the characters of the Madagascar form except 

 that they are still less diflferent from what I have called the typical form. 



Widely distributed. Australia and New Caledonia, Formosa, China, Siam, Arabia, Madagascar, 

 Lake N'Gami, Senegal. 976. 



I. 74.— Genus GRAPHODERES. 



Coxal lines fine but distinct : supra-articular border moderately broad ; middle 

 femora with rather short, stout setae. Elytra uniformly speckled with black and 

 yellow. 



The eleven species form two groups, the first represented only by a single species : — 



1. Form rather depressed; thorax and head without any distinct black marks. 



No. 1084. 



2. Form rather convex ; thorax and head with very distinct black marks. 



Nos. 1085 to 1094. 



Group 1. 



1084. Dytiscus liberus, Say, Hydaticus liber, M.C — Ovalis, parum elon- 

 gatus, fere depressus, nitidus, ferruginous, prothorace ad latera elytrisque testaceis, 

 his creberrime nigro-vermiculatis. Long. 12, lat. 7 m.m. 



In the male the front tarsi are provided beneath with three larger j^alettes of 

 unequal size, and sixteen smaller but still highly developed ones. The middle 

 tarsi have the basal joint just perceptibly thickened, and furnished beneath with 

 four palettes — two outer and two inner — while the second joint bears only two 

 palettes, which are placed at its outer margin. 



The species has much resemblance to a species of Rhantus, from which a glance 

 at the ciliate hind margins of the posterior tarsi will, of course, distinguish it : it 

 varies somewhat in size, but not much in other respects. 



United States of North America, from Vancouvei-'s Land to New York and Florida. 989. 



Gkoup 2. 



1085. Hydaticus austriacus, Sturm, M.C. — Nitidus, testaceus, vertice, signaturis 

 frontalibus prothoracisque fasciis duabus magnis, nigris, elytris creberrime nigro- 

 vermiculatis ; elytrorum epipleuris pone medium per-angustis ; tarsis posterioribus 

 gracilibus. Long. 13, lat. vix, 8 m.m. 



