﻿6P0NGIIDA. 
  433 
  

  

  spoagologist 
  to 
  whose 
  keen 
  eye 
  for 
  generic 
  characters 
  we 
  owe 
  this 
  

   very 
  distinct 
  and 
  constant 
  genus. 
  

  

  lOTROCHOTA 
  *, 
  g. 
  n. 
  

   Halickondria, 
  pars, 
  Higgin, 
  Boioerhank, 
  Carter. 
  

  

  Desmacidinidne 
  with 
  smooth 
  linear 
  skeleton-spicules 
  and 
  minute 
  

   birotulate 
  llesh-spicules 
  with 
  straight 
  shafts, 
  both 
  the 
  heads 
  being 
  of 
  

   the 
  same 
  size, 
  circular, 
  and 
  symmetrical 
  ; 
  sarcode 
  purple. 
  

  

  This 
  genus 
  is 
  formed 
  to 
  include 
  Ualichondria 
  hirotulata, 
  Higgin 
  

   (Ann. 
  & 
  Mag. 
  Nat. 
  Hist. 
  1877, 
  xix. 
  p. 
  296) 
  and 
  Halicliondria 
  pur- 
  

   pureri^ 
  Bowerbank 
  (P. 
  Z. 
  S. 
  1875, 
  p. 
  293). 
  HaUchondria 
  s. 
  str. 
  is 
  

   based 
  on 
  a 
  Reaiorid. 
  The 
  peculiar 
  tlesh-spicule 
  of 
  this 
  genus 
  is 
  one 
  

   form 
  of 
  the 
  flesh-spicule 
  which 
  usually 
  appears 
  in 
  the 
  Hesmacidi- 
  

   nidte 
  under 
  the 
  form 
  of 
  an 
  " 
  anchorate," 
  equi- 
  or 
  inequi-anchorate. 
  

   The 
  latter 
  forms 
  apparently 
  originate 
  by 
  exeentric 
  flexion 
  of 
  the 
  

   shaft 
  of 
  a 
  birotulate 
  form 
  like 
  the 
  present, 
  and 
  suppression 
  of 
  the 
  

   rays 
  which 
  lie 
  on 
  that 
  side 
  towards 
  which 
  the 
  shaft 
  is 
  bent 
  ; 
  the 
  thin 
  

   expansions 
  unitiug 
  the 
  arms 
  in 
  the 
  birotulate 
  apparently 
  become 
  

   the 
  " 
  falces 
  " 
  which 
  unite 
  the 
  arms 
  of 
  the 
  anchorate 
  (see 
  Carter, 
  

   Ann. 
  & 
  Mag. 
  Nat. 
  Hist. 
  1874, 
  xiv. 
  p. 
  207). 
  An 
  intermediate 
  stage 
  

   is 
  seen 
  in 
  Chrondrodadia 
  — 
  viz. 
  C. 
  virgnta, 
  Wyville 
  Thomson, 
  and 
  

   C. 
  {Halicliondria) 
  abi/ssi, 
  Carter 
  (Vosmaer), 
  — 
  the 
  shaft 
  of 
  the 
  bii'otu- 
  

   late 
  being 
  bent 
  and 
  the 
  arm 
  of 
  that 
  side 
  almost 
  aborted 
  as 
  in 
  a 
  normal 
  

   anchorate 
  (see 
  Carter, 
  torn. 
  cit. 
  p. 
  218), 
  Cliondrodadia 
  differs 
  further 
  

   from 
  lotrochota 
  in 
  being 
  accompanied 
  by 
  a 
  bihamate 
  or 
  tricurvate 
  

   flesh-spicule. 
  Cladorrhiza, 
  8ars 
  (C. 
  ahi/ssicola, 
  id. 
  Some 
  Hemark. 
  

   Forms 
  &c. 
  i. 
  p. 
  Go, 
  pi. 
  vi. 
  figs. 
  lG-34), 
  is 
  an 
  allied 
  form, 
  but 
  not 
  

   only 
  has 
  the 
  shaft 
  of 
  the 
  birotulate 
  bent, 
  and 
  the 
  symmetry 
  of 
  the 
  

   head 
  impaired 
  by 
  the 
  almost 
  total 
  reduction 
  of 
  that 
  arm 
  of 
  the 
  head 
  

   which 
  thus 
  comes 
  into 
  contact 
  with 
  the 
  curve 
  of 
  the 
  shaft, 
  but 
  it 
  is 
  

   ineqai-hirotulate, 
  and 
  corresponds 
  in 
  the 
  birotulate 
  series 
  to 
  the 
  in- 
  

   equianchorate 
  form 
  of 
  the 
  anchorates 
  of 
  the 
  common 
  types 
  of 
  Desma- 
  

   cidinid;e 
  ; 
  it 
  differs 
  from 
  lotrochota 
  in 
  the 
  possession 
  of 
  a 
  bihamate 
  

   flesh-spicule 
  in 
  addition 
  to 
  the 
  birotulate. 
  

  

  It 
  is 
  noteworthy 
  that 
  those 
  species 
  of 
  this 
  genus 
  hitherto 
  known 
  

   are 
  from 
  shallow 
  water 
  (littoral, 
  see 
  below), 
  while 
  all 
  other 
  known 
  

   allied 
  forms 
  except 
  Axos 
  ancJiorata, 
  Carter, 
  for 
  which 
  the 
  depth 
  is 
  

   not 
  given, 
  are 
  from 
  the 
  deep 
  sea. 
  

  

  From 
  an 
  unusually 
  well-preserved 
  specimen 
  of 
  the 
  green 
  variety 
  

   of 
  I. 
  purpurea 
  from 
  the 
  Amirante 
  Islands 
  (see 
  Pt. 
  II. 
  of 
  this 
  Eeport), 
  

   I 
  am 
  able 
  to 
  make 
  out 
  that 
  the 
  ciliated 
  chambers 
  are 
  oval, 
  the 
  ends 
  

   being 
  well 
  rounded, 
  and 
  measure 
  -032 
  by 
  '025 
  millim. 
  They 
  are 
  

   crowded 
  along 
  the 
  sides 
  and 
  in 
  the 
  parenchyma, 
  lying 
  between 
  what 
  

   ap])ear 
  to 
  be 
  secondary 
  and 
  tertiary 
  canals 
  of 
  the 
  excretory 
  system, 
  

   and 
  also 
  (though 
  this 
  may 
  perhaps 
  be 
  merely 
  apparent) 
  upon 
  the 
  

  

  * 
  From 
  lov. 
  a 
  violet, 
  and 
  T-pnyos, 
  a 
  wheel, 
  in 
  allusion 
  to 
  the 
  purple 
  colour 
  and 
  

   the 
  birotulate 
  flesh-spicules. 
  

  

  2ir 
  

  

  