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



sometimes there is only a scarcely visible elevation bear- 

 ing two or three setae, while in other cases there is a 

 strongly-elevated plica, the extremity of which projects 

 backwards to a greater or less extant as a free spine. 



I have been quite unable to arrange the numerous 

 variations in such a way as to indicate distinct species ; 

 nevertheless it may prove that there is more than one 

 truly distinct species mixed under the name. In South 

 America the last ventral segment is apparently always 

 simple, and in North America is never quite simple, but 

 always more or less distinctly carinate or subspinose ; in 

 Mexico and Central America there exists a great deal of 

 variation in this character. 



29. Hydrophilus dorsalis, Brulle. 

 Brulle, Voy. d'Orb., p. 57, pi. 4, f. 61. 

 Hydrophilus limbalis, Lee, Proc. Ac. Phil., 1865, 



p. 367. 

 America, North and South. Arizona, California, New 

 Grenada, Peru ; Chili, Corrientes (teste Brulle). 



So far as I can see, this insect is only different from 

 H. lateralis by the greater extension of the yellow colour 

 of the upper surface, the lateral band of the wing-case 

 occupying about two-fifths of the width, and at the base 

 nearly always extending inwards towards the scutellum. 



If I may express an opinion, from the few specimens 

 I have seen, I should say that, as in H. lateralis, the last 

 ventral segment has its carina more developed in North 

 America than in South America. 



Group 9. Upper surface without a yellow cincture ; epi- 

 pleural margin with rather fine and somewhat distant 

 punctures at or behind the middle, but without sculpture 

 at the shoulder. (Species 30 to 32). 



The three species I have here associated are separated 

 from Group 7 merely as a matter of convenience in 

 determining the species ; T. xanthopus, in fact, has not 

 the epipleurae quite impunctate at- the base, careful 

 examination revealing fine punctures on this part. 



