These curious little beetles are very active in the water; they 
swim with ease and walk tolerably well. The subulated api- 
cal joint of the palpi and the remarkable shield-formed plate, 
distinguish this group from all the other Dyticidse, but La- 
treille was wrong in supposing the antennae were composed 
only of ten joints. The following are British species. 
* Thorax subquadrate . 
1. elevatus Panz. 14, 9. 
May, running brooks, Letheringsett, Norf.; and Bexley, Kent. 
** Thorax broadest at the base . 
2. mucronatus Lea. — Ste.pl. 11,./. 1.— ophthalmicus Kirb. 
Suffolk, Bottisham and near Swansea. 
3. parallelus Bab., Trans. Ent. Soc. 1 . p. 178. pi. 15. f 5. 
Taken at Cambridge. 
4. ferrugineus Paylc. Curt. B. E. pi. 730. — fulvus Fab. — Ent. 
Trans. 1 .pi. 15. f. 4.— interpunctatus Mars. 
I quite agree with Mr. Babington, that this is not the D. 
ferrugineus of Linn. ; his words “ferrugineus totus” better 
agree with Hyphydrus ferrugineus , as does also his observa- 
tion which follows, “ Magnitudine Cimicis, totus rufus s. 
ferrugineus.” Paykull, however, gave the name of ferrugi- 
neus to this Haliplus before Fabricius and Marsham noticed 
it, I have consequently retained his name. 
April, ditches and ponds, Wandsworth Common; August, 
Norfolk, Cambridge, and Loch Fad. 
5. rubicundus Spe. — Bab. E. T. 1 5.f. 6. — subnubilus Bab. 
E. T. 1 . pi. 1 5.f. 3. var . Common everywhere. 
6. ruficollis DeGeer. — minutus Don. 2. pi. 68. I and 2. 
April, ponds and ditches near London, Norfolk, and Cam- 
bridge. 
7. affinis Step. — The specimens I have received from corre- 
spondents thus named are merely small vars. of ruficollis. 
8. obliquus Bl. — Pz. 14. 6. — amcenus Olio. 3. t. B.f. 50. 
Near London, Norfolk and Cambridge. 
9. confinis Kirb. Step. 
April, Wandsworth Common ; Aug., Norfolk and Suffolk. 
10. lineatocollis Mars. — Ahr. 7. 3. — muticus Gyll. — bistrio- 
latus Duft. 
April, Norfolk, Suffolk, Cambridge ; Wandsworth Com- 
mon ; Aug., Whittlesea Mere ; Sept., ponds, Paddington. 
11. marginepunctatus Panz. 14. 10. 
Near London, and ponds of Botanic Garden, Cambridge. 
12. melanocephalus Steph. 13. brevis Kirb. 
14. impressus Fab. — Panz. 14. 7. — flavicollis Mars. — caesus 
Duft. 
April, ponds and ditches, Norfolk and Battersea fields ; 
July, Wandsworth Common. 
The plant is Ceratophyllum demersum , Common Hornwort. 
