﻿A 
  MONOGRAPH 
  OF 
  THE 
  VICTORIAN 
  SPONGES. 
  57 
  

  

  skill 
  (pseiicloderm) 
  pierced 
  by 
  the 
  numerous, 
  closely 
  placed 
  pseudopores. 
  The 
  

   pseudopores 
  are 
  nearly 
  circular 
  and 
  rather 
  small, 
  ranging 
  up 
  to 
  about 
  0*54 
  mm. 
  in 
  

   diameter, 
  they 
  are 
  abundant 
  on 
  the 
  sides 
  of 
  the 
  sponge 
  but 
  rare 
  on 
  the 
  upper 
  surface. 
  

   On 
  the 
  upper, 
  flattened 
  surface 
  of 
  the 
  colony 
  are 
  numerous 
  good-sized 
  oscula, 
  each 
  

   surrounded 
  by 
  a 
  very 
  well 
  developed 
  oscular 
  fringe, 
  and 
  averaging 
  about 
  3 
  mm. 
  

   in 
  diameter. 
  The 
  largest 
  specimen 
  in 
  the 
  collection 
  is 
  represented 
  in 
  Figure 
  7, 
  

   Plate 
  II. 
  It 
  is 
  about 
  110 
  mm. 
  in 
  height, 
  and 
  over 
  50 
  mm. 
  in 
  its 
  lesser 
  horizontal 
  

   diameter 
  at 
  the 
  top. 
  Unfortunately 
  the 
  specimen 
  had 
  to 
  be 
  cut 
  to 
  make 
  it 
  go 
  into 
  

   the 
  bottle, 
  so 
  its 
  greater 
  horizontal 
  diameter 
  cannot 
  be 
  determined. 
  The 
  colour 
  in 
  

   spirit 
  is 
  white. 
  

  

  Full 
  details 
  of 
  the 
  canal-system 
  are 
  given 
  on 
  pp. 
  29, 
  30. 
  It 
  belongs 
  to 
  the 
  

   " 
  reversed 
  " 
  type 
  (type 
  C) 
  and 
  is 
  illustrated 
  in 
  Figures 
  1, 
  2, 
  Plate 
  V. 
  The 
  peculiar 
  

   " 
  yellow 
  granules," 
  which 
  seem 
  to 
  be 
  characteristic 
  of 
  the 
  species, 
  are 
  described 
  and 
  

   their 
  nature 
  discussed 
  on 
  p. 
  18 
  et 
  seq. 
  (PI. 
  VI., 
  Figs. 
  -1, 
  5.) 
  

  

  {b.) 
  Arrnngcmcnt 
  of 
  the 
  Skeleton. 
  — 
  The 
  skeleton 
  consists 
  mainly 
  of 
  triradiate 
  

   spicules 
  lying 
  in 
  a 
  rather 
  confused 
  layer 
  in 
  the 
  mesoderm 
  (PI. 
  VI., 
  Fig. 
  6). 
  A 
  

   good 
  many 
  quadriradiates 
  are 
  also 
  present, 
  with 
  the 
  apical 
  rays 
  as 
  usual 
  projecting 
  

   into 
  the 
  gastral 
  cavities 
  of 
  the 
  Ascon-tubes. 
  A 
  very 
  few 
  oxeotes 
  also 
  occur 
  in 
  boiled 
  

   out 
  preparations. 
  

  

  (c.) 
  The 
  Spicules 
  (PI. 
  IX., 
  Fig. 
  4). 
  

  

  (1) 
  Triradiates.- 
  — 
  Dermal. 
  Eegular. 
  Piays 
  conical, 
  tapering 
  a 
  little 
  more 
  

   suddenly 
  towards 
  the 
  apex, 
  which 
  is 
  fairly 
  sharp, 
  measuring 
  about 
  

   0-16 
  by 
  0-014 
  mm. 
  Deep. 
  The 
  same 
  as 
  the 
  dermal, 
  but 
  with 
  the 
  

   rays 
  perhaps 
  a 
  little 
  stouter. 
  

  

  (2.) 
  Quadriradiates. 
  — 
  Like 
  the 
  triradiates 
  but 
  with 
  a 
  small 
  apical 
  rav, 
  

   which 
  is 
  slender, 
  gradually 
  sharply 
  pointed 
  and 
  slightly 
  curved. 
  

  

  (3.) 
  Oxeotes. 
  — 
  These 
  are 
  rare, 
  small, 
  asymmetrically 
  fusiform, 
  generally 
  

   slightly 
  and 
  irregularly 
  curved, 
  measuring 
  about 
  0*2 
  by 
  0.0083 
  mm. 
  

  

  {d.) 
  Affinities. 
  — 
  Mr. 
  Carter's 
  description 
  of 
  this 
  species 
  is 
  not 
  very 
  satisfactory, 
  

   as 
  he 
  mistook 
  the 
  true 
  nature 
  of 
  the 
  arrangement 
  of 
  the 
  canal 
  system, 
  stating 
  that 
  

   the 
  oscula 
  arc 
  '' 
  only 
  in 
  communication 
  with 
  the 
  dilated 
  parts 
  oi 
  the 
  interspaces," 
  

   whereas, 
  as 
  we 
  have 
  seen, 
  they 
  are 
  really 
  true 
  oscula 
  and 
  what 
  Mr. 
  Carter 
  considered 
  

   as 
  interspaces 
  are 
  gastral 
  cavities. 
  The 
  very 
  peculiar 
  reversal 
  of 
  the 
  canal 
  system 
  is 
  

   extremely 
  misleading, 
  and 
  this 
  doubtless 
  gave 
  rise 
  to 
  Mr. 
  Carter's 
  error. 
  Comparison 
  

   with 
  a 
  piece 
  of 
  one 
  of 
  Mr. 
  Carter's 
  type 
  specinuuis 
  kindly 
  sent 
  to 
  me 
  from 
  the 
  

   British 
  Museum 
  has 
  con\inced 
  me 
  that 
  my 
  specimens 
  are 
  identical 
  with 
  Mr. 
  Carter's 
  

   Clathrina 
  cavata. 
  

  

  