﻿SPONGIIDA. 
  625 
  

  

  TETBACTINELLIDA. 
  

  

  As 
  usual 
  with 
  shallow 
  dredgings 
  like 
  those 
  of 
  he 
  ' 
  Alert,' 
  the 
  

   family 
  Choristidte 
  is 
  alone 
  represented. 
  The 
  proportion 
  of 
  species 
  

   to 
  the 
  rest 
  of 
  the 
  collection 
  is 
  about 
  the 
  same 
  as 
  in 
  the 
  Australian 
  

   collection 
  ; 
  but 
  we 
  miss 
  the 
  genera 
  Geodia 
  and 
  Placospongla, 
  which 
  

   might 
  have 
  been 
  expected 
  to 
  occur 
  here. 
  The 
  remarkable 
  group 
  with 
  

   discoid 
  dermal 
  plates 
  which 
  stands 
  between 
  Geodia 
  and 
  SteUetta 
  is 
  

   represented 
  by 
  a 
  new 
  species. 
  

  

  CHOEISTID^. 
  

  

  4U. 
  Tetilla 
  dactyloidea. 
  

  

  Tethya 
  dactyloidea, 
  Carta-, 
  Ann. 
  4" 
  Ma(/. 
  N. 
  H. 
  1869, 
  iii. 
  p. 
  15, 
  figs, 
  

   1-5 
  ; 
  1872, 
  ix. 
  p. 
  82, 
  pi. 
  10. 
  figs. 
  1-5. 
  

  

  A 
  somewhat 
  imperfect 
  specimen, 
  having, 
  however, 
  probably 
  had 
  

   somewhat 
  the 
  form 
  of 
  Tlienea 
  tvalliclii, 
  "Wright, 
  when 
  perfect^t. 
  c. 
  

   not 
  produced 
  upwards 
  into 
  the 
  long 
  cylinder 
  figured 
  by 
  Mr. 
  Carter, 
  

   but 
  depressed 
  and 
  agariciform. 
  Its 
  diameter 
  is 
  much 
  greater 
  

   than 
  that 
  of 
  Carter's 
  specimen, 
  viz. 
  40 
  millim. 
  (1| 
  inch); 
  its 
  pre- 
  

   sent 
  height 
  is 
  25 
  millim. 
  (1 
  inch). 
  The 
  spicules 
  agree 
  closely 
  with 
  

   Mr. 
  Carter's 
  descriptions 
  and 
  figures, 
  with 
  the 
  exception 
  that 
  the 
  

   forked 
  anchor 
  does 
  not 
  exhibit 
  a 
  constant 
  inequality 
  in 
  the 
  length 
  

   of 
  the 
  arms. 
  

  

  Hah. 
  Glorioso 
  Islands, 
  low 
  water. 
  

  

  Distribution. 
  S.E. 
  coast 
  of 
  Arabia 
  (^Carter). 
  

  

  ERYLUS, 
  Gray. 
  

  

  SteUetta, 
  pars, 
  Schmidt, 
  Spony. 
  Aclr. 
  Meer., 
  Spong. 
  Kilst. 
  Alt/., 
  Spong. 
  

  

  Atl. 
  Get. 
  ; 
  Carter, 
  Ann. 
  ^ 
  Mag. 
  N. 
  H. 
  1880, 
  v. 
  p. 
  135. 
  

   Erylus 
  and 
  Triate, 
  Gray, 
  P. 
  Z. 
  8. 
  1867, 
  p. 
  549. 
  

   Discifera, 
  of 
  subsection 
  Pycnodermata 
  of 
  group 
  Stellettina, 
  Carter, 
  

  

  Ann. 
  ^ 
  Mag. 
  N. 
  H. 
  1883, 
  xi. 
  p. 
  348. 
  

  

  I 
  have 
  already 
  indicated 
  (Part 
  I. 
  pp. 
  471, 
  472) 
  that 
  the 
  species 
  

   called 
  by 
  Schmidt 
  SteUetta, 
  but 
  provided 
  with 
  disks 
  composed 
  of 
  

   modified 
  trichites, 
  should 
  be 
  definitely 
  separated 
  from 
  that 
  genus. 
  

   I 
  adopt 
  for 
  this 
  distinct 
  group 
  the 
  generic 
  term 
  which 
  Dr. 
  Gray 
  

   assigned 
  to 
  S. 
  mamillaris, 
  Schmidt. 
  It 
  may 
  be 
  characterized 
  as 
  : 
  — 
  

   Comprising 
  Choristid 
  Tetractinellida 
  with 
  the 
  surface 
  covered 
  by 
  a 
  

   layer 
  of 
  detached 
  discoid 
  trichite 
  globates, 
  and 
  having 
  besides 
  a 
  zone- 
  

   spicule 
  and 
  small 
  stellates 
  with 
  slender 
  and 
  few 
  rays. 
  Form 
  

   lobate. 
  Vents 
  single 
  or 
  multiple. 
  

  

  It 
  differs 
  from 
  Geodia 
  in 
  the 
  discoid 
  form 
  of 
  the 
  trichite 
  masses 
  

   and 
  their 
  independence 
  of 
  each 
  other 
  (in 
  Geodia 
  they 
  are 
  united 
  by 
  

   ligaments). 
  It 
  includes 
  the 
  described 
  species 
  SteUetta 
  euastrion, 
  S. 
  

   mamiUaris, 
  and 
  S. 
  discophora, 
  Schmidt, 
  and 
  S. 
  eiiastrum, 
  Carter. 
  

   SteUetta 
  (jeodina 
  and 
  S. 
  intermedia, 
  Schmidt, 
  should 
  be 
  referred 
  to 
  

   Qeodia. 
  

  

  2s 
  

  

  