96 Mr. D. Sharp's revision of the species 



much curved away from the body, and is quite as long 

 as the space between the middle and hind coxse. The 

 pubescent space on the base of the hind femur is of 

 moderate size, covering about one-fourth of the whole 

 area of the lower face. The tooth on the claw of the 

 middle and hind feet of the male is placed quite near the 

 apex, and there is no other external mark of distinction 

 between the sexes, so far as I can observe. The last 

 ventral segment is unarmed, except that there exist 

 two or three elongate setse in the middle near the hind 

 margin. The uniformity in structure of the species 

 appears very complete, and if it were not for the absence 

 of intermediate forms they might all be considered as 

 varieties of one widely-distributed species. 



As regards the peculiarity on which I have specially 

 based the group, I may remark that it was first pointed 

 out by Leconte, and that one effect of the peculiarity is 

 to allow a more complete contraction of the prothorax on 

 to the after-body, owing to the raised mesosternal keel 

 being able to pass slightly beyond the front margin of 

 the fissured prosternum. The group will no doubt 

 ultimately be treated as a distinct genus. 



1. Tropisternus Scutellaria, Cast. 



Cast., Hist. Nat., ii., p. 54. 



Hydrophilus lepidus, Brulle, Voy. d'Orb., Ins., p. 57. 



Brazil. (Buenos Ayres). 



This species is very closely allied to Hydrophilus 

 collaris, but the metallic lines on the wing-cases are 

 extremely diminished, and, indeed, are represented only 

 by four small, short streaks placed near the suture, two 

 just behind the middle and two near the extremity ; one 

 or more of these small streaks is occasionally quite 

 obliterated. The epipleural margin is provided with 

 punctures which, although they do not reach to the 

 shoulder, are more distinct in front than they are in 

 //. collaris. The under or inner claw on each of the 

 middle and hind feet is in the male dentate near the 

 extremity ; this is the only external sexual character I 

 can detect. 



This species appears to be rare. 



