6G 



(March, 



sexes of nil four. The commonest species with us are ahdaceus and bipunctatus, 

 both of which are about equally common, simiatns is less common, and minutits 

 decidedly scarce. 



Sydrohius picicrus seem? to be a good species ; it used to be very common in 

 the marshes of the Yare, below Norwich, wlicre it occurred quite unmixed with 

 H. fuscipes proper, indeed, I have only become acquainted with the latter within 

 the last year or two, and have never taken the two species in company. 



Limnius troglodytes : I have taken a few specimens of a Limnius here, which 

 I believe to be this species ; the engraved lines on the thorax are straight, and the 

 elytral striae are finely and, as a rule, closely punctured. Three of my specimens 

 came from the river Wensum, a few miles above Norwich, and I found another 

 amongst about a score of L. tuberculattis from the Dilham Canal, at Horning. The 

 smallest of my specimens is •06 in length, and the largest nearly equal in size to an 

 average specimen of tuberculatua. Unfortunately, in " The Coleoptera of the 

 British Islands " (vol. iii, p. 378) the characters laid down in the table of species 

 are at variance with those in the detailed descriptions ; as L. rivularis is said in 

 the table to have the thorax more shiny than tuberculatus, but in the description of 

 the former we are told that the disc of the thorax is more closely punctured and 

 duller than in the latter. I have no doubt, however, that my determination of the 

 species is correct. 



In this neighbourhood one lias exceptional facilities for the study of Oyrinus 

 marinus and opacus, and there really seems to be no adequate reason for treating 

 the latter as merely a variety of the former ; certainly, with us opacus is very con- 

 stant in its characters, and in the river Wensum, in the immediate neighbourhood 

 of Norwich, it occurs in the utmost profusion, quite unmixed with any other species. 

 The two species jlast named are the commonest of the genus with us, both being 

 much commoner than natator. G. elongattis has doubtless done duty for O. bicolor 

 in more important collections than my own, but when we have before us a specimen 

 of the latter, really possessing the characters assigned to the species, it is impossible 

 not to be struck with its distinctness. I have examined one such example taken by 

 Mr. Thoulcss, at Hickling Broad, in company with G. minutus ; it is considerably 

 larger than than tlie largest elongatus, with the external angle of the elytra com- 

 pletely rounded, and the mesosternum black ; in my long series of elongatus the 

 narrower and more convex examples are rather below the average size for the 

 species, and all have the external angle of the elytra well marked, and the meso- 

 sternum red. 



131, Rupert Street, Norwich : 

 January 16th, 1890. 



[Mr. Edwards' criticism as to the discrepancy between my table and descrip- 

 tion of Limnius is a perfectly just one ; I have, as a rule, been very careful to avoid 

 such discrepancies, as I have myself found them a considerable trouble, even in the 

 works of most careful authors like Thomson, Weise, &c., &c. ; this is the first to 

 wliich I have had my attention called ; in the ease alluded to, I find that specimens 

 of the two species difJer inter se, and that the character is itself variable ; this, I 

 take it, is the usual explanation of such discrepancies, as the tables and descriptions 

 are not always drawn up at the same time. — W. W. F.] 



