On Aquatic Carnivorous Coleoptera or Dytiscidw. 835 



thought it justifiable under these circumstances to use the name for the aggregate 

 in which the species just referred are included, but as Motschoulsky never attempted 

 any definition of Hydrocoptus, and included under it both Hydroporides and 

 Noterides, his name had better not be cited in connection with it. 



I. 4.— Genus PROXOTERUS. {Vide p. 263.) 



The unique species is of small size ; its individuals only attain 2 m.m. of length, 

 and their appearance is that of a small parallel Noterus. The anterior tibise are 

 short and broad, and their outer angle is distinctly spinose ; at the inner angle 

 they have a minute spur, and a second more elongate one, this latter is curved : 

 the basal joint of the front tarsus is a good deal incrassate. and elongate. The 

 last joint of the labial palpus is dilated ; the presternum is straight from the front 

 margin to the end of the prosternal process; this is of moderate size, with its ter- 

 minal angles rounded, but is truncate at the extremity : the interior laminae of the 

 hind coxae approach very close to the middle coxae, and the wings of the metasternum 

 are quite small ; the suture separating them from the hind coxae is quite distinct. 

 The coxal processes are almost truncate, their outer angle being scai'cely at all pro- 

 duced ; the coxal cavities are almost contiguous, and no evidence of their not being 

 absolutely so can be seen without dissection. The swimming legs are moderately 

 well developed, the tibiae being very distinctly flattened and incrassate, so as to be 

 much broader than the tarsi, these latter are a little longer than the tibiae, their 

 basal joint elongate, considerably longer than the three following ones together ; 

 the two claws are short, and rather stout, equal, curved. 



This is an interesting form, apparently intermediate between Hydrocoptus and 

 Noterus : it has quite the appearance of the Hydrocopti. 



I. 5.— Genus SYNCHORIUS. {Vide p. 264.) 



This aggregate consists of six species, Avhose individuals have the appearance of 

 small Noteri, but when a punctuation is present on the wing-cases it is of a very 

 peculiar kind, and gives rise to an appearance of asperities, rather than of round 

 depressions. The antennae are slender with the terminal joints more elongate tlian 

 the basal ones. The anterior tibiae are rather slender, with the outer margin 

 densely set with very short thick ciliae, the outer apical angle has almost disappeared, 

 the inner one is furnished with a slender elongate curved spur, or hook : the basal 

 joint of the front tarsus is very largely developed. The prosternal process is short, 

 broad, very rounded behind, and is as it were continued forwards between the coxae 

 to near the front margin of the thorax, and becomes quite gradually and gently 

 obsolete there. The suture between the hind coxa and metasternum nearly .touches 

 the middle coxa ; the coxal processes are much developed, and produced at their 

 outer angles ; the hind coxal cavities are contiguous ; the swimming legs are 



TBANS. ROY. DHB. SOC, N.S., VOL. n. 5 p 



