﻿MELOLONTHID.E 
  OF 
  THE 
  UNITED 
  STATES. 
  265 
  

  

  separate' 
  genus, 
  but 
  the 
  preceding 
  species 
  is 
  intermediate 
  in 
  the 
  last 
  mentioned 
  

   peculiarity,' 
  and 
  the 
  former 
  is 
  altogether 
  a 
  sexual 
  mark. 
  The 
  sixth 
  ventral 
  segment 
  

   is 
  large, 
  and 
  "projects 
  downwards; 
  it 
  is 
  smooth 
  and 
  flat 
  on 
  its 
  anterior 
  surface, 
  strong- 
  

   ly 
  punctured 
  and 
  hairy 
  on 
  the 
  posterior 
  surface, 
  which 
  is 
  convex, 
  and 
  nearly 
  hori- 
  

   zontal 
  ; 
  the 
  line 
  where 
  the 
  two 
  surfaces 
  meet 
  is 
  armed 
  at 
  the 
  middle 
  with 
  two 
  large 
  

   sharp 
  teeth. 
  

  

  4. 
  DIPLOTAXES. 
  

   This 
  group 
  established 
  by 
  Kirby, 
  but 
  first 
  defined 
  as 
  a 
  sub-group 
  by 
  Lacordaire, 
  

   contains 
  species 
  of 
  small 
  size, 
  forming 
  the 
  transition 
  from 
  the 
  groups 
  with 
  transverse 
  

   not 
  prominent 
  anterior 
  costse, 
  to 
  those 
  with 
  the 
  coxae 
  conical. 
  The 
  thorax 
  is 
  almost 
  

   always 
  furnished 
  with 
  an 
  apical 
  membranous 
  margin, 
  a 
  character 
  not 
  known 
  to 
  me 
  

   in 
  any 
  other 
  group 
  except 
  Dichelonychae, 
  which 
  differ 
  by 
  the 
  chelate 
  ungues. 
  Bur- 
  

   meister's 
  group 
  of 
  Schizonychae 
  should 
  probably 
  enter 
  here, 
  as 
  they 
  differ 
  only 
  by 
  the 
  

   greater 
  depth 
  of 
  the 
  emargination 
  of 
  the 
  labrum, 
  and 
  the 
  less 
  breadth 
  of 
  the 
  ligula 
  : 
  

   the 
  former 
  is 
  indeed 
  not 
  free 
  from 
  variation 
  in 
  our 
  species 
  of 
  Diplotaxis. 
  It 
  has 
  not 
  

   escaped 
  the 
  attentive 
  eye 
  of 
  Lacordaire 
  that 
  the 
  ventral 
  sutures 
  are 
  distinct 
  in 
  this 
  

   group, 
  not 
  effaced 
  at 
  the 
  middle 
  as 
  in 
  Rhizotrogi 
  ; 
  but 
  he 
  mentions 
  that 
  exceptions 
  in 
  

   this 
  respect 
  are 
  found 
  in 
  Erapecta 
  : 
  as 
  that 
  genus 
  has 
  no 
  apical 
  margin 
  of 
  membrane 
  

   on 
  the 
  thorax, 
  I 
  am 
  in 
  doubt 
  whether 
  it 
  might 
  not 
  be 
  more 
  naturally 
  placed 
  in 
  

   Rhizotrogi. 
  

  

  A 
  character 
  not 
  noted 
  by 
  previous 
  authors, 
  which 
  seems 
  to 
  distinguish 
  this 
  group, 
  

   is 
  the 
  entire 
  coalescence, 
  without 
  perceptible 
  suture 
  between 
  the 
  5th 
  ventral 
  segment 
  

   and 
  the 
  propygidium 
  ; 
  I 
  know 
  of 
  no 
  other 
  group 
  in 
  which 
  this 
  takes 
  place, 
  and 
  taken 
  

   in 
  conjunction 
  with 
  the 
  small 
  pygidium, 
  the 
  disappearance 
  of 
  the 
  sixth 
  ventral 
  segment, 
  

   the 
  distinctness 
  of 
  the 
  ventral 
  sutures, 
  and 
  the 
  prominence 
  of 
  the 
  anterior 
  coxae, 
  it 
  

   would 
  seem 
  to 
  render 
  this 
  as 
  distinctly 
  limited 
  as 
  the 
  other 
  groups 
  here 
  recognized. 
  

  

  Our 
  genera 
  may 
  be 
  thus 
  distinguished 
  : 
  — 
  

  

  Ungues 
  antici 
  dente 
  parum 
  prominulo 
  apicali, 
  posteriores 
  fissi 
  - 
  - 
  - 
  Orsonyx 
  Lee. 
  

  

  Ungues 
  omnes 
  conformes 
  : 
  

  

  Palpi 
  maxillares 
  articulo 
  ultimo 
  ovali 
  Diplotaxis 
  Kirby 
  

  

  Palpi 
  maxillares 
  articulo 
  ultimo 
  elongato, 
  eylindrico 
  - 
  - 
  - 
  - 
  Alobus 
  Lee. 
  

  

  Orsonyx 
  Lee. 
  

  

  Corpus 
  oblongum, 
  paulo 
  convexum, 
  alatum 
  ; 
  clypeus 
  margine 
  rcflexo, 
  late 
  rotundatus 
  medio 
  subsinuatus, 
  

   sutura 
  frontali 
  distincta. 
  Labrum 
  concavum, 
  modice 
  emarginatum 
  ; 
  mandibula? 
  validaj 
  prominulas 
  ; 
  maxillae 
  

   mala 
  exteriore 
  ad 
  apicem 
  bidentata; 
  (palpi 
  desunt). 
  Mentum 
  trapezoideum, 
  ligulas 
  latae 
  connatum, 
  antice 
  

   se 
  micirculariter 
  depressum 
  ; 
  palpi 
  labiales 
  laterales; 
  antennae 
  breves 
  10-articulatae, 
  clava 
  parva 
  triphylla. 
  

   Thorax 
  ad 
  apicem 
  membranula 
  coriacea 
  marginatus, 
  linea 
  marginali 
  nulla. 
  Tibiae 
  anticae 
  tridentatae 
  unical- 
  

   caratae, 
  posteriores 
  extus 
  bicoronatas, 
  ad 
  apicem 
  paulo 
  incrassatae, 
  fosticae 
  intus 
  dense 
  pilosae; 
  tarsi 
  tibiis 
  vix 
  

   longiores, 
  setosi 
  ; 
  unguiculis 
  anticis 
  dente 
  tenui 
  acuto 
  subapicali 
  parum 
  prominulo 
  armatis, 
  posterioribus 
  fissis, 
  

   parte 
  inferiore 
  latiore 
  acuto 
  subtruncato 
  vix 
  breviorc 
  : 
  propygidium 
  fere 
  omnino 
  tectum. 
  

  

  68 
  

  

  