Mr. G. W. Kirkalily on Aquatic Rhynchoti. 57 



Ventral surface entirely black, except the connexivum, which 

 is sordid testaceous, the junctures of the segments narrowly 

 black. 



Long. 16-16"7 niilliin, ; lafc. pronot. 6 milliin. 



Ngan Hoei, llo-Chan (China) : Montandon's collection 

 and mine (kindly presented by Prof. Montundon). N. Ciiina : 

 British Museum. 



Tlio species of the family Notonectldjc are exceedingly 

 difficult to diagnose satisfactorily separately ; the structural 

 characters are very obscure and not always constant ; more- 

 over, such characters as the punctuation of tlie head and 

 pronotum (wiiicli, in coiijuiiction with others, are used so 

 extensively in other families of the Rliynchota) appear to be 

 quite valueless here. The coloration of the hemielytra as a 

 diagnostic character is here not only valueless, but even 

 misleading. Almost the only satisfactory method loft is the 

 comparative, and tliat ceases to be satisfactory when one does 

 not possess the other species necessary for comparison ! 



Montandoni is structurally very close to both tn'guttata 

 and chinensis] the hemielytra of the two latter, however, 

 appear to be somewhat laterally sinuate and slightly dilated 

 at the lateral margins of the corium, about one third of its 

 length from its own apex ; there is not the slightest trace of 

 this in Montandoni. 



In chinensis the head is very much narrower towards the 

 base ; from the base the lateral interior margins of the eyes 

 keep almost parallel for a little space, then diverge (but not 

 much) ; tlie vertex in this species is more than three times as 

 Avide as the narrowest part of the head (close to the base) ; in 

 triguttala the head is wider basally than in chinensis and is 

 not so widely divergent, the above-mentioned margins of the 

 eyes are sensibly curved, and the vertex is a trifle more than 

 two and a half times as wide as the narrowest part of the 

 head ; in Montandoni the head is wider both at the vertex 

 and base, and the interior margins of the eyes are much 

 straighter. 



From the above notes it may perhaps appear that Mon- 

 tandoni is intermediate between trigidtata and chinensis; 

 but, from an exhaustive examination of a number of specimens 

 of all three species, I am convinced that such is not the case ; 

 although Montandoni and chinensis are so similar in colour, 

 it is rather triguttata that is the intermediate species. 



I have much pleasure in dedicating this large and hand- 

 some species to my learned colleague Professor Montandon, 

 who has helped in such a great degree, from his wide expe- 

 rience and extensive labours, to increase our knowledge of 



