﻿230 
  Mr, 
  G. 
  R. 
  Waterhouse 
  on 
  the 
  

  

  specimens 
  of 
  the 
  true 
  clongatus 
  mixed 
  with 
  others 
  of 
  

   H. 
  angustalus, 
  

   3. 
  Ilydrochus 
  anguslatus, 
  Muller, 
  Germak, 
  Mulsamt, 
  Ste- 
  

   phens. 
  — 
  More 
  commonly 
  known 
  on 
  the 
  Continent 
  hy 
  

   the 
  name 
  of 
  H. 
  cretiatus, 
  it 
  being 
  generally 
  supposed 
  

   to 
  be 
  the 
  Elophorus 
  crenatus 
  of 
  Fabricius 
  ; 
  but 
  Erichson 
  

   has 
  discovered 
  that 
  the 
  Fabrician 
  insect 
  is 
  the 
  Latridius 
  

   porcatus. 
  

   H. 
  Brevis 
  is 
  at 
  once 
  known 
  by 
  its 
  short 
  form. 
  H. 
  elongntus 
  and 
  

   angustalus 
  have 
  nearly 
  the 
  same 
  form, 
  but 
  may 
  be 
  distinguished 
  — 
  

   H. 
  elongatus 
  by 
  the 
  alternate 
  interstices 
  of 
  the 
  striae 
  of 
  the 
  elytra 
  

   being 
  carinated, 
  and 
  //. 
  angustalus 
  by 
  the 
  interstices 
  being 
  even, 
  

   or 
  very 
  nearly 
  so. 
  H. 
  clongatus 
  is 
  common 
  in 
  the 
  fens 
  of 
  Whit- 
  

   tlesea 
  Mere, 
  and, 
  I 
  believe, 
  is 
  not 
  found 
  in 
  the 
  London 
  district. 
  

   H. 
  angustalus 
  is 
  very 
  common 
  in 
  ponds 
  and 
  ditches 
  in 
  the 
  neigh- 
  

   bourhood 
  of 
  London. 
  

  

  The 
  British 
  species 
  of 
  Ochtheb'ius 
  which 
  have 
  come 
  under 
  my 
  

   notice 
  are: 
  — 
  

  

  1. 
  Ochthehms 
  marinus, 
  of 
  Stephens 
  as 
  well 
  as 
  the 
  German 
  

  

  and 
  French 
  authors. 
  

  

  2. 
  Ochtheb'ius 
  ceneus, 
  Waterhouse, 
  Stephens. 
  

  

  I 
  am 
  satisfied 
  this 
  is 
  a 
  good 
  species, 
  but 
  I 
  do 
  not 
  find 
  it 
  de- 
  

   scribed 
  by 
  the 
  continental 
  Entomologists. 
  It 
  approaches 
  most 
  

   nearly 
  to 
  O. 
  marinus 
  and 
  0. 
  j)ygmceus. 
  From 
  either 
  it 
  may 
  be 
  

   distinguished 
  by 
  its 
  broader 
  form 
  and 
  peculiar 
  colouring, 
  as 
  well 
  

   as 
  by 
  the 
  striae 
  of 
  the 
  elytra 
  being 
  more 
  delicately 
  punctured, 
  

   more 
  widely 
  separated, 
  and 
  the 
  punctures 
  less 
  closely 
  packed 
  to- 
  

   gether. 
  From 
  O. 
  marinus 
  it 
  moreover 
  differs 
  in 
  wanting 
  the 
  two 
  

   transverse 
  impressions 
  on 
  the 
  thorax, 
  and 
  the 
  disc 
  of 
  the 
  thorax 
  

   being 
  distinctly 
  punctured 
  ; 
  that 
  these 
  punctures 
  are 
  much 
  scat- 
  

   tered, 
  and 
  consequently 
  not 
  very 
  numerous, 
  furnishes 
  another 
  

   point 
  of 
  distinction 
  when 
  0. 
  ceneus 
  is 
  compared 
  with 
  0. 
  2»Jgniceus, 
  

   whicli 
  has 
  the 
  thorax 
  thickly 
  and 
  comparatively 
  strongly 
  punctured. 
  

   The 
  head 
  is 
  black, 
  tinted 
  with 
  green, 
  and 
  so 
  is 
  the 
  thorax, 
  but 
  

   the 
  lateral 
  margins 
  are 
  testaceous 
  yellow 
  ; 
  the 
  elytra 
  are 
  testaceous 
  

   yellow, 
  with 
  a 
  golden 
  aeneous 
  tinge 
  usually, 
  but 
  sometimes 
  without 
  

   the 
  metallic 
  colour. 
  The 
  suture 
  is 
  brownish 
  or 
  dusky. 
  I 
  took 
  

   this 
  species 
  many 
  years 
  back 
  in 
  the 
  ponds 
  of 
  Putney 
  Heath 
  in 
  the 
  

   month 
  of 
  May. 
  

  

  