fi90 On Aquatic Carnivorous Coleoptera or DytiscidcB. 



108 J. Sandracottus nauticus, d. sp. — Ovalis, sat latus et convesus, nitidus, niger, 

 capite elytrisque nigi-o testaceoque variegatis, thorace ad latera testaceo ; elytrorum 

 signaturis testaceis baud magnis. Long. 14i, lat. 82 m.m. 



In this species there are three series of black marks on the head, the vertex 

 being black, and in front of it two large black marks, not quite connected to one 

 another, but confluent with the black at the inner margin of the eye, while in front 

 of these two marks there is another angular dark mark. The thorax is black with 

 the sides yellow. The elytra are black with yellow marks transversely disposed on 

 them, viz., three basal small spots, an elongate but narrow humeral mark emitting 

 behind a prolongation towards the middle, two marks just behind the middle placed 

 so as to form an interrupted transverse band, a subapical oblique mark, and a 

 minute apical spot ; the yellow colour of the humeral mark is prolonged backwards 

 along the outer margin to juot beyond the post-medial mark, but becomes towards 

 its termination a little separated from the margin. 



I have seen only one individual of this form, and a variety in which the yellow 

 spots on the elytra are greatly reduced in size : it is considerably smaller than 

 Hydaticus maculatus, Wehncke, and rather different in form, being not so narrow 

 in front, and the yellow colour along the margin of the elytra is much less prolonged 

 in the posterior direction. 



Borneo. 987. 



1082. Hydaticus maculatus, Wehncke, Stet. Ent. Zeit. XXXVII, p. 196. — 

 Major, ovalis, latiusculus, anterius angustatus, parum convexus, subtus piceus, 

 supra niger, capite elytrisque nigro testaceoque variegatis, thorace ad latera 

 testaceo ; elytrorum signaturis testaceis baud magnis. Long \bh, lat. 8| m.m. 



The front of the head is yellow, the vertex is largely black, on the middle are two 

 large black marks, which are connected, and so extended as to reduce the yellow 

 colour between them and the vertex to a transverse line, or even in extreme cases 

 to two small spots ; there is a vaguely defined dark angular mark in front of these 

 marks, on each wing-case there are three small basal spots and an elongate humeral 

 mark yellow, this latter giving off" near its extremity a prolongation inwards ; just 

 beyond the middle there are variable yellow spots, sometimes forming an irregular 

 transverse band, there is also a small, subapical, oblique mark, and a quite minute 

 spot at the tip yellow : the yellow colour of the humeral mark extends backwards 

 along the outer margin as far as the oblique subapical mark. The spots of yellow 

 colour are very variable, never extensive, they are sometimes reduced to a few 

 sraall specks ; the yellow marginal colour is however apparently subject to little or 

 no variation in its extent. The female seems to be rather larger than the male. 



The Malay peniusuh.. 988. 



