﻿364 
  COLLECTIONS 
  FROM 
  MELANESIA, 
  

  

  37. 
  Psilacal)aria 
  gracillima. 
  

   (Plate 
  XXXVII. 
  figs. 
  D-D" 
  ; 
  Plate 
  XXXVIII. 
  figs./-/".) 
  

  

  Corallum 
  extremely 
  delicate, 
  erect, 
  branching 
  dichotomously, 
  

   approximately 
  in 
  one 
  plane, 
  and 
  at 
  approximately 
  right 
  angles. 
  

   Apparently 
  no 
  anastomosis. 
  Internodcs 
  12-16 
  millim. 
  long, 
  diameter 
  

   •3 
  to 
  '7 
  millim., 
  cylindrical, 
  slightly 
  flexuous. 
  Soft 
  joints 
  incon- 
  

   spicuous, 
  not 
  broader 
  than 
  the 
  adjacent 
  internodes. 
  Axis 
  of 
  inter- 
  

   nodes 
  hard, 
  white, 
  not 
  striated. 
  

  

  Cortex 
  about 
  one 
  quarter 
  the 
  thickness 
  of 
  the 
  whole 
  branch, 
  rough- 
  

   ened 
  by 
  the 
  large 
  spicules. 
  Verrucee 
  arranged 
  in 
  spiral 
  series, 
  with 
  

   bases 
  almost 
  in 
  contact 
  on 
  larger 
  branches, 
  rather 
  distant 
  and 
  on 
  

   opposite 
  sides 
  on 
  the 
  smaller 
  ones 
  ; 
  triangular 
  and 
  flattened 
  in 
  the 
  

   former, 
  low, 
  rounded, 
  and 
  tubercular 
  in 
  the 
  latter 
  ; 
  basal 
  diameter 
  

   and 
  height 
  1 
  millim. 
  in 
  the 
  large 
  to 
  "5 
  millim. 
  in 
  the 
  small 
  branches. 
  

   Colour 
  of 
  cortex 
  white, 
  of 
  tips 
  of 
  verrucas 
  pale 
  yellow. 
  

  

  Spicules 
  of 
  general 
  cortex: 
  — 
  (i.) 
  Large 
  cylindro-fusiform 
  to 
  sub- 
  

   clavate, 
  with 
  thick 
  axis, 
  slightly 
  tapering 
  to 
  round-pointed 
  ends, 
  well 
  

   provided 
  with 
  strong 
  tubercles 
  about 
  '03 
  millim. 
  high, 
  either 
  sub- 
  

   spherical 
  or 
  forming 
  low 
  roughened 
  ridges 
  often 
  extending 
  round 
  as 
  

   much 
  as 
  one 
  quarter 
  of 
  the 
  circumference 
  of 
  the 
  spicule 
  (appai'ently 
  

   representing 
  tubercular 
  whorls 
  of 
  those 
  spicules 
  of 
  other 
  Melithseidae 
  

   which 
  possess 
  them) 
  ; 
  size 
  -28 
  to 
  '31 
  by 
  '087 
  millim. 
  ; 
  tubercles 
  

   commonly 
  more 
  abundant 
  and 
  larger 
  near 
  one 
  end 
  than 
  the 
  other, 
  

   (ii.) 
  Smaller, 
  fusiform, 
  with 
  sharply 
  pointed 
  ends 
  and 
  prominent 
  

   pointed 
  and 
  roughened 
  tubercles, 
  more 
  or 
  less 
  curved, 
  scattered 
  

   abundantly 
  all 
  over 
  ; 
  size 
  -21 
  to 
  '25 
  by 
  -OoS 
  to 
  "071 
  millim. 
  (also 
  at 
  

   base 
  of 
  verrucee) 
  [probably 
  young 
  forms 
  of 
  (i.)]. 
  Spicules 
  of 
  verrucae 
  : 
  — 
  

   (iii.) 
  Similar 
  to 
  (i.), 
  but 
  with 
  less 
  broad 
  and 
  ridge-like 
  tubercles, 
  

   measuring 
  as 
  much 
  as 
  '3 
  by 
  "087 
  millim. 
  ; 
  on 
  exterior 
  of 
  the 
  verrucae, 
  

   except 
  just 
  at 
  the 
  apex, 
  (iv.) 
  Subclavate, 
  tapering 
  from 
  a 
  broad 
  to 
  

   a 
  sharp-pointed 
  end, 
  well 
  covered 
  with 
  irregularly 
  scattered, 
  pro- 
  

   minent, 
  pointed 
  tubercles, 
  which 
  become 
  larger 
  towards 
  the 
  broad 
  

   end, 
  where 
  they 
  project 
  forwards 
  beyond 
  and 
  in 
  the 
  direction 
  of 
  

   the 
  axis 
  of 
  the 
  spicule 
  ; 
  on 
  the 
  inner 
  wall 
  of 
  the 
  verrucae, 
  thus 
  

   resembling 
  the 
  subapical 
  verruca-spicules 
  of 
  Acaharia 
  divaricata. 
  

   (v.) 
  Smaller, 
  fusiform, 
  with 
  fewer 
  tubercles, 
  pointed, 
  scattered 
  

   equally 
  all 
  over, 
  two 
  or 
  three 
  terminal 
  ones 
  at 
  one 
  end 
  prolonged 
  

   much 
  as 
  in 
  (iv.) 
  ; 
  size 
  "21 
  to 
  '25 
  by 
  "035 
  to 
  '044 
  millim. 
  ; 
  on 
  apex 
  of 
  

   verrucae 
  [probably 
  young 
  forms 
  of 
  (iv.)]. 
  (vi.) 
  Intermediate 
  forms 
  

   between 
  (i.) 
  and 
  (ii.), 
  with 
  tubercles 
  more 
  distinct 
  and 
  smaller 
  than 
  

   in 
  (i.) 
  ; 
  size 
  '31 
  by 
  "07 
  millim. 
  ; 
  on 
  general 
  body 
  of 
  zooid. 
  

  

  Of 
  all 
  these 
  six 
  forms 
  I 
  only 
  distinguish 
  3 
  distinct 
  types, 
  viz. 
  : 
  — 
  

   (i.) 
  [including 
  iii. 
  and 
  vi.] 
  representing 
  the 
  large 
  cortical 
  fusiform 
  of 
  

   other 
  Mclithaeidae, 
  but 
  found 
  also 
  on 
  the 
  verruca, 
  from 
  the 
  fact 
  of 
  

   the 
  latter 
  being 
  covered 
  more 
  or 
  less 
  with 
  what 
  represents 
  the 
  

   general 
  cortex 
  ; 
  (ii.) 
  representing 
  the 
  smaller 
  cortical 
  fusiform 
  and 
  

   perhaps 
  also 
  the 
  horizontal 
  verruca-spicule 
  of 
  other 
  Melithoeidae 
  ; 
  

   (iii.) 
  [including 
  v.] 
  representing 
  the 
  longitudinal 
  verruca-spicule, 
  

  

  