576 
ME.  E.  F.  TOMES  OX  A  XEW  GEXUS  OF 
Otov.  1893, 
affinities  of  this  curious  form  would  have  probably  remained  in  great 
obscurity.  The  thick  walls,  as  such,  have  entirely  disappeared,  and 
no  wall  either  thick  or  thin  is  present,  the  septa  of  one  calice 
being  continuous  with  those  of  another,  just  as  in  Thamnastrcea 
and  Clavsastrceci.  (See  Pi.  XX.,  tig.  1.) 
The  ornamentation  of  the  sides  of  the  septa  is  resolved  into  pseudo- 
synapticulae,  having  the  character  of  those  observed  in  the  genus 
Clausastrceci. 
Several  elongated  calices  furnish  unquestionable  proof  that  fissi- 
parity  took  place,  the  operation  being  clearly  observable  in  a  more 
or  less  advanced  state.  (See  PI.  XX.,  fig.  2.) 
There  are  also  a  few  calices  which,  though  almost  full-sized,  are 
so  nearly  circular,  and  which  encroach  so  visibly  on  the  others,  that 
they  can  only  have  been  caused  by  extra-calicular  budding.  (See 
PI.  XX.,  fig."  6.) 
The  septa  and  their  connecting  costae  consist  of  a  single  trabecule, 
as  in  AstrceomorpJia. 
The  septal  costae  are  much  swollen,  and,  coming  into  contact  with 
each  other  laterally,  are  fused  together  between  the  calices,  where 
there  would  be  a  wall  in  the  Astraeidae,  and  the  swollen  part  of  each 
has  a  central  portion,  which,  being  more  dense,  is  opaque  when 
seen  by  transmitted  light,  and  is  consequently  quite  dark  in  thin 
section.  This  lateral  fusing  of  the  septal  costae  gives  solidity  and 
strength  to  the  corallum,  and  in  reality  takes  the  place  of  a  wall. 
All  parts  of  the  septal  apparatus,  including  the  columella,  are 
composed  of  lines  of  granules  passing  upward  and  outward,  very 
much  like  the  webs  of  a  feather. 
There  are  a  few  weak  and  straight  dissepiments  between  the  septa. 
The  pseudo-synapticulae  are  numerous,  have  little  prominence,  and 
appear  on  the  sides  of  the  septa  as  continuous  horizontal  ledges, 
greatly  resembling  those  of  Clausastrcea.  (See  PI.  XX.,  tig.  4.) 
They  are  formed  by  the  continuation  outward  at  regular  intervals 
of  the  lines  of  granules  of  which  the  septa  are  formed,  and  were 
mistaken  by  Prof.  Duncan  for  mere  lines  of  ornamentation. 
The  columella  is  large  and  formed  by  lines  of  granules  passing 
upward  and  outward;  into  it  all  the  primary  septa  pass,  and  blend 
without  any  evidence  of  the  point  of  union. 
The  full  number  of  primary  septa  in  a  large  calice  is  ten. 
I  name  and  define  the  genus  of  which  the  present  species  is  the 
sole  representative  as  follows  : — 
Genus  Stelidioseris,  gen.  nov.1 
Corallum  compact,  small,  globose,  or  tuber-shaped,  the  corallites 
radiating  more  or  less  regularly  from  a  basal  point  of  attachment. 
There  is  no  wall  between  the  corallites,  the  septa  being  continuous 
between  them.  The  septa  are  imperforate,  each  consisting  of  a  single 
1  [I  had  originally  selected  the  name  Styloseris  ;  but  after  the  paper  had  been 
read,  it  was  pointed  out  to  me  that  the  name  was  pre-occupied,  and  I  have 
therefore  substituted  Stelidioseris  for  it. — July  15th,  1893.] 
