322 
DE.  J.  S.  BOWEEBAKK  ON  THE  ANATOiTT 
same  description  as  that  represented  by  figure  48.  From  its  general  character,  I am 
inclined  to  believe  that  it  belongs  to  the  sarcode. 
Spinulato-ensifoem  (Plate  XXVI.  fig.  49). — I have  never  found  this  spiculum  in  situ. 
A few  specimens  were  obtained  from  the  same  sponge  from  which  the  spiculum  repre- 
sented by  fig.  48  was  taken. 
Acuate  : BASALLY  EECTANGULATED  (Plate  XXVI.  fig.  50). — I obtained  this  spiculum 
from  the  spongeous  matter  scraped  from  the  base  of  Oculina  rosea,  by  a dealer  in  the 
process  of  cleaning  the  coral.  It  is  not  a malformation,  as  there  are  several  of  them  in 
the  same  slide,  and  they  are  all  angulated  to  the  same  extent.  It  is  probably  an  internal 
defensive  spiculum. 
SuBSPiNULATO-AECUATE  (Plate  XXVI.  fig.  51). — I obtained  this  singular  form  of  spicu- 
lum from  my  friend  Mr.  Thomas  Ijstgall,  a zealous  and  hberal  investigator  of  the  Spon- 
giadse.  It  is  said  to  be  from  Ash  Island,  New  South  Wales.  When  well-developed, 
both  the  terminations  of  the  cylindrical  shaft  are  more  or  less  spinulate,  and  one  or  both 
of  the  ends  of  the  shaft  are  incipiently  spinous. 
The  nearest  form  to  this  spiculum  is  the  arcuate  one  that  is  found  on  the  surface  of 
the  gemmule  of  Spongilla  lacustris,  Johhstoh,  and  it  is  probable  that  this  one  is  also 
from  a sponge  of  that  genus,  as  I have  never  seen  any  spicula  of  that  form  in  any  maiine 
sponge  from  Australia. 
Explahatioh  of  the  Plates. 
PLATE  XXIII. 
Structure  of  Spicula. 
Fig.  I.  Distal  termination  of  a porrecto-ternate  spiculum  fr’om  Tetliea  cranium,  with 
angular  distortions  from  external  pressure,  x260  hnear:  page  282. 
Fig.  2.  A portion  of  an  adult  spiculum  from  Spongilla  flumatilis,  chaiTed  to  exhibit  the 
thin  membrane  of  the  central  cavity  of  the  spiculum,  x260  linear:  page  282. 
Fig.  3.  A portion  of  an  immature  spiculum  from  Spongilla  lacustris,  charred  to  exhibit 
the  dense  membrane  lining  the  large  central  cavity  in  the  young  spiculum,  i 
X 260  linear:  page  282.  . i 
Fig.  4.  A section  at  right  angles  to  the  axis  of  the  upper  part  of  the  shaft  of  a ternate  : 
spiculum  from  Geodia  Barretti,  Boweebahx,  MS.,  exhibiting  the  concentric  i 
layers,  x260  linear:  page  282.  ! 
Figs.  5 and  6.  Portions  of  charred  spicula  from  the  skeleton  fasciculi  of  Tetliea  cranium,  | 
exhibiting  their  hollow  condition  after  incineration,  x90  linear:  page  283.  ; 
Fig.  7.  A portion  of  a spiculum  from  Euplectella  aspergillum,  slightly  charred,  exlii-  I 
biting  the  concentric  layers  of  silex,  X 90  linear:  page  284.  j 
Fig.  8.  A portion  of  an  adult  spiculum  from  the  skeleton  of  Geodia  IBAndrewii,  | 
