227 



half of the elytra) the larger punctures also are very sparse and 

 without seriate arrangement. 



Queensland ; sent by Mr. DeVis. 



HYDROCHUS. 



The description of the Australian members of this genus are so 

 scattered through the literature of widely separated countries 

 that it seems desirable to furnish some notes showing their 

 relation to each other. I have therefore attempted to place their 

 characters intelligibly in a tabular form, adding some remarks 

 on some of them, and giving a detailed description of a new 

 species. There is, however, one species that I have been unable 

 to identify, viz., R. ohsmiroceneus^ Fairm. I should judge from 

 the description that it is near H. Horni, Blackb., but it may be 

 at once distinguished from that insect by its having a fovea in 

 the middle of the head between the eyes as well as by the well- 

 defined sculpture of its prothorax and the implication that the 

 alternate interstices of its elytra are not more elevated than the rest. 

 I have before me a specimen which Mr. Lea tells me that he 

 has ascertained by comparision with the type to be H. parallelus, 

 Macl. 



A. General colour dull-brown, pitchy, or obscurely seneous. 

 B. Head not trisulcate between the eyes. 

 C. Seriate punctures of the elytra so coarse 

 as to leave no continuously defined 

 interstices between some of the rows Adelaid'ji, Blackb. 

 *CC. Interstices between the rows of elytral 

 punctures not obscured by the coarse- 

 ness of the punctures, 

 D. Alternate elytral interstices strongly 

 carinate, in strong contrast to the 

 others ... ... ... ... Victoruv,, Blackb. 



DD. Alternate elytral interstices not, or 

 only feebly, more elevated than the 

 others. 

 E. Prothorax at base with four well- 

 defined impressions separated by 

 well-defined ridges ... ... re^w/am, Blackb. 



EE. Base of prothorax not having four 

 well-defined impressions. 

 F. Clypeus much more nitid and less 

 coarsely punctured than the rest 

 of the head (size comparatively 

 large) ... ... ... diver sicepSy Blackb. 



FF. Clypeus punctured like the rest 



of the head (size very small)... Horni, Blackb. 

 BB. Head distinctly trisulcate between the 

 eyes. 



* In H. Victorke some of the interstices are ill defined, but it is on> 

 account of rugulosity of sculpture, the punctures not being particularly 

 large. 



