1914. 133 



As regards the sedeagus (figs. 3) its study in this species is rendered 

 somewhat difficult by its frequent immaturity, which not only gives rise 

 to some shrivelling in dried specimens, but also renders it difficult to 

 discriminate the chitinised from the membranous parts of the tube, a 

 difficulty which is increased by the fact that there is but little difference 

 in the coloration of the membrane and the chitin, the latter never 

 becoming very dark in G. natator. The median lobe has the bulbous 

 basal part rather narrow, and the apical or rod-like half rather broad, 

 and departing but little from being parallel-sided. The chitinisation 

 of the ventral aspect is considerable at the tip, so that the median 

 orifice cannot extend to the extremity, but there is no elevation of the 

 hard par! s that limit the orifice. 



Gr, NATATOR vai\ 11. OBLITUS. 



G. natatoris proxime affinis, sed minor, elytrorum sculptura minus obsoleta, 

 interstitiis intends versus apicem subconvexis. Long. 5-j mm. 



Two specimens, approaching so closely to natator that their dis- 

 tinctness may be doubted, though on comparison with a series of 200 

 examples I find no others like them. One has been in my collection, as 

 a variety of G. suffriani, for many years. The other is the specimen 

 the eedeagus of which was figured as that of G. natator ( Sharp 

 and Muir, Tr. Ent, Soc, London, 1912, pi. xlix, fig. 42). This 

 var. must be very near to wankowiczi, Reg. 



The eedeagus (figs. 4) is within what I have treated as the limits 

 of variation of na,tator ; the median lobe is slightly narrower and its 

 outline slightly more sinuous. 



The type specimen was found in the River Ouse at Stony Stratfor* 

 in September, 1868. The other example I have lost the locality of ; it 

 sculpture, and its form even, differ a little from the other. Mr. Edwards 

 has an intermediate specimen. 



4. Gr. SUFFRIANI. 



(?) G. suffriani, Scriba, Stettin, ent. Zeit., 1855, p. 280. 



The individuals of this species are as a rule smaller than natator, but 

 in this respect the two overlap. Although large suffriani are extremely 

 similar to small 'natator, yet the two are easily enough distinguished : the 

 punctures of the inner striae at the base are more distinct than in na- 

 tator, and the underside is much darker in colour ; the inflexed margins 

 of the elytra, the mesosternum, and even the last ventral segment are 

 never bright red. Variations in sculpture occur that may give rise to 

 some confusion, but when the strise of punctures at the base of the 



