320 



On Aquatic Carnivorous Coleoptera or Dytiscidce. 



Posterior 



coxal cavities 



destitute of 



coxal exci- • 



sion, and 



extra-rimal 



lobe. 



Ventral seg-~) 

 inent sol- 

 dered to 

 liorder of 

 posterior 

 coxae. 



First ventral 

 segment 

 free, not- 

 soldered to 

 the coxae. 



Scutellum I 

 exposed. J 



Hind coxal cavi- 

 ties separated, 

 not all protects 

 ed by the ad- 

 pressed coxal 

 processes. 



Hind coxal cat- 

 ties nearly or 

 quite contigu- 

 ous, being pro- 

 longed inwards 

 above the coxal 

 processes, and 

 ■so protected by 

 the latter. 



Mesosternum placed 

 nearly on the same 

 plane as the nieta- 

 stenium and there- 

 fore much exposed 

 between this and the 

 prothorax ; its epi- 

 meron very narrow, 

 sublinear, and indis- 

 tinct. J 



Mesosternum placed") 

 at an angle with the 

 metastenium and 

 thusmuch concealed; 

 its epimeron tri- 

 angular and distinct. J 



BlUESSINI. 



{VideY>. 336.) 



HVPHYDRINI. 



( Vide p. 370.) 



STERNOPRISCUS. 

 (F«/ep. 384.) 



Hydroporini. 

 ( Vide p. 389.) 



CELINA. 

 (Videy). 487.) 



II. 6. — Group Hydrovatini. 



Prosternal process almost triangular, its posterior margin forming the base of the 

 triangle, hind coxal cavities not contiguous, with broad coxal processes incised behind 

 by a distinct coxal excision, external to which is a free, prominent, portion of the 

 process (= extra-rimal lobe,) 



There are only two genera included in this family ; they may be readily dis- 

 tinguished as below, one is an autogenus, the other is rich in species. 



Coxal excision longer in the longitudinal than 

 in the transverse direction ; labrum 

 visibly exserted. Numerous species. 



Coxal excision .shorter in the longitudinal than ] 



the transverse direction ; only the I 



labiiim visible. A single ] 



species. J 



in 

 fringes of 



HYDROVATUS. 

 {Vide p. 321.) 



QUEDA. 

 {Vide p. 336.) 



