﻿British 
  Species 
  of 
  Microciona, 
  Bk. 
  103 
  

  

  Megasdera* 
  three, 
  viz. 
  : 
  — 
  1. 
  Long, 
  slightly 
  curved 
  styles, 
  

   sometimes 
  very 
  slightly 
  constricted, 
  sometimes 
  slightly 
  swollen 
  

   above 
  the 
  base, 
  and 
  studded 
  at 
  the 
  base 
  with 
  round 
  tubercles 
  

   or 
  blunt 
  spines 
  about 
  *34 
  to 
  '48 
  millim. 
  x 
  "009 
  millirn. 
  (fig. 
  A, 
  

   2). 
  2. 
  Entirely 
  (but 
  generally 
  somewhat 
  sparsely) 
  spined, 
  

   straight 
  or 
  slightly 
  curved 
  styles, 
  gradually 
  tapering, 
  basally 
  

   truncate 
  to 
  subtylote, 
  varying 
  much 
  in 
  size, 
  about 
  # 
  08 
  to 
  

   •204 
  millim. 
  x 
  "0075 
  millim. 
  (fig. 
  A, 
  3). 
  3. 
  Long, 
  slender, 
  

   smooth 
  styles, 
  slightly 
  clavate, 
  about 
  "22 
  to 
  *308 
  millim. 
  x 
  

   •0035 
  millim. 
  (fig. 
  A, 
  4). 
  

  

  Microsclera 
  two, 
  viz. 
  : 
  — 
  1. 
  Very 
  slender 
  toxa, 
  having 
  the 
  

   ends 
  much 
  produced 
  and 
  the 
  tips 
  sharply 
  spined, 
  very 
  various 
  

   in 
  size, 
  ranging 
  from 
  about 
  *048 
  to 
  "29 
  X 
  "0025 
  millim. 
  

   (fig. 
  A, 
  5). 
  2. 
  Minute 
  palmate 
  isochelaj, 
  palmre 
  subtrian- 
  

   gular, 
  comparatively 
  rare, 
  length 
  *008 
  to 
  "012 
  millim., 
  ave- 
  

   rage 
  about 
  *0i05 
  millim. 
  (fig. 
  A, 
  6). 
  

  

  For 
  comparison 
  measurements 
  are 
  appended 
  of 
  the 
  corre- 
  

   sponding 
  spicules 
  of 
  Microciona 
  armata, 
  taken 
  from 
  a 
  speci- 
  

   men 
  found 
  coating 
  red 
  sandstone 
  on 
  the 
  shore 
  at 
  Sidmouth, 
  

   S. 
  Devon. 
  This 
  sponge 
  appears 
  to 
  be 
  somewhat 
  rare, 
  and 
  its 
  

   occurrence 
  on 
  rock 
  between 
  tide-marks, 
  if 
  not 
  previously 
  

   noticed, 
  is 
  of 
  some 
  interest, 
  the 
  specimens 
  mentioned 
  by 
  Dr. 
  

   Bowerbank 
  (Mon. 
  Brit. 
  Spong. 
  vol. 
  ii. 
  pp. 
  130, 
  131) 
  being 
  

   on 
  shells 
  and 
  apparently 
  from 
  deeper 
  water. 
  

  

  Megasclera. 
  — 
  1. 
  Stout, 
  basally 
  tuberculated 
  or 
  spined 
  

   styles, 
  mainly 
  two 
  sizes, 
  with 
  fewer 
  intermediates, 
  one 
  size 
  

   ranging 
  from 
  about 
  - 
  23 
  to 
  '35 
  millim. 
  in 
  length, 
  the 
  other 
  

   from 
  about 
  '53 
  to 
  "627 
  millim. 
  long 
  ; 
  breadth 
  in 
  both 
  cases 
  

   about 
  '02 
  millim. 
  (fig. 
  B, 
  2). 
  2. 
  Spined 
  styles 
  of 
  the 
  very 
  

   characteristic 
  form 
  described 
  and 
  figured 
  by 
  Dr. 
  Bowerbank 
  

   (Mon. 
  Brit. 
  Spong. 
  vol. 
  ii. 
  pp. 
  129, 
  130, 
  131, 
  and 
  141, 
  and 
  

   vol. 
  iii. 
  pi. 
  xxiii. 
  fig. 
  24), 
  *16 
  to 
  '2 
  x 
  "016 
  millim. 
  at 
  base 
  

   (fig. 
  B, 
  3) 
  : 
  there 
  are 
  also 
  some 
  smaller 
  ones 
  only 
  about 
  "008 
  

   millim. 
  in 
  diameter. 
  3. 
  Slender 
  styles 
  about 
  *312 
  to 
  *428 
  

   x 
  -0065 
  millim. 
  (see 
  " 
  Note," 
  Explanation 
  of 
  PI. 
  VI.). 
  

  

  Microsclera. 
  — 
  1. 
  Toxa 
  quite 
  smooth 
  at 
  tips, 
  *022 
  to 
  '19 
  X 
  

   about 
  "0025 
  millim. 
  (fig. 
  B, 
  5). 
  2. 
  Palmate 
  isochelaj, 
  abun- 
  

   dant, 
  generally 
  '013 
  to 
  *017 
  millim. 
  in 
  length, 
  a 
  very 
  few 
  

   observed 
  '0215 
  to 
  "023 
  millim. 
  long 
  (fig. 
  B, 
  6). 
  

  

  It 
  will 
  be 
  seen, 
  from 
  a 
  comparison 
  of 
  the 
  spicular 
  measure- 
  

  

  clay-boulder 
  about 
  "low-water 
  mark" 
  in 
  company 
  with 
  a 
  variety 
  of 
  

   Hijmeniacidon 
  Dujardinii, 
  Bk., 
  of 
  a 
  jet-h\&ck 
  colour 
  when 
  fresh. 
  — 
  C. 
  

  

  * 
  The 
  names 
  of 
  the 
  spicules 
  are 
  in 
  accordance 
  with 
  Ridley 
  and 
  Dendy's 
  

   nomenclature 
  in 
  their 
  Report 
  of 
  the 
  ' 
  Challenger 
  ' 
  Monaxonida, 
  part 
  fix. 
  

   (1887). 
  

  

  