_ On Aquatic Carnivorous Coleoptera or DytiscidcB. 861 



T. 34.— Genus HEROPHYDRUS. {Vide p. 392.) 

 Six species form this aggregate ; the individuals are of large size (comparatively 

 with many other Hydroporides), from 4 to 6 m.m. of length : they are oblong- 

 oval in form, very convex beneath ; without pubescence, coarsely punctate ; the 

 head is either margined in front, Avith the margin interi'upted in the middle, or is 

 without margin ; the fourth joint of the front tarsus is but little elongate in com- 

 parison with the others, which are narrow in proportion to their length, the third 

 joint only obscurely bilobed, and the insertion of the iourth joint is nearer to the 

 apical than to the basal edge of the third joint ; the front tibise are short, and 

 rather broad ; the ridge on the inner face of the elytra is largely developed, risino- 

 gradually from the front towards the extremity till its greatest prominence is 

 attained, and then falling abruptly, so that as regards one of its sides (the posterior) 

 it forms a ligula, but as regards the other does not : the genicular area of the 

 epipleurae is limited externally by a well-marked line ; the hind legs are slender ; 

 their coxae formed as in Ccelambus. 



The genus is nearly allied to Ccelambus, but differs b}'- the elytral ridge, as well 

 as by the shorter, and comparatively broad, front tibias ; the shape of the tibite 

 suggests an approximation to Hydrovatus, which is confirmed by the rather small 

 front tarsi, as well as by the swimming legs, slender and ill-developed in proportion 

 to the weight and size of the insect. 



Madagascar is the metropolis of the aggregate, three species being peculiar to 

 that island, while the other three are found in neighbouring regions, — two in South 

 Africa, these two the most Ccelambus like — ; while the sixth species has an exten- 

 sive range, being found in Arabia, Senegal, Egypt and North Africa, and Southern 

 Europe. 



I. 35.— Genus CCELAMBUS. {Vide p. 394.) 

 This is an extensive aggregate, consisting of about fifty species ; the individuals 

 are convex beneath, but in other respects somewhat variable in form, usually 

 oblong-oval, but sometimes shorter, even rotund in form ; they are nearly or entirely 

 destitute of pubescence, the upper surface is usually pale, with distinct black marks, 

 the under surface nearly always with coarse, (or moderately coarse) punctuation. 

 There is always a distinct, and abrupt ligula on the inner face of the elytra, and 

 the genicular area of the epipleura is well defined, and generally limited externally 

 by a more or less raised line : the epipleurse are greatly reduced in breadth in their 

 posterior portion, in fact opposite the hind margin of the second ventral segment 

 there exists nothing of the epipleura but its two marginal lines, which have become 

 contiguous. The front border of the hind coxae has much extension in the anterior 

 direction, (especially in the elongate species constituting the greater part of the 

 genus), and the culmen or summit of its arch is narrow, and in extreme cases 



est 



