Vol.  49.] 
AFFINITIES  OF  THE  GENTJS  ASTROCCENIA. 
569 
42.  Observations  on  the  Affinities  of  the  Genus  Astrocgenia. 
By  Bobert  E.  Tomes,  Esq.,  E.G.S.  (Bead  June  21st,  1893.) 
[Plate  XX.] 
Besearches  recently  made  relative  to  the  structure  of  certain 
undoubted  Astrocoenice ,  having  for  their  primary  object  the  better 
understanding  of  the  supposed  species  of  the  genus  obtained  from 
the  Glamorganshire  Conglomerate,  have  been  productive  of  results 
which  are  to  a  great  extent  unexpected,  and  which  will  lender 
imperative  a  complete  modification  in  the  classificatory  position  of 
the  genus. 
Before  recording  the  examinations  which  have  led  to  these  results, 
it  is  desirable  that  I  should  make  a  brief  survey  of  some  part  of 
the  literature  relating  to  the  genus.  Commencing  with  its  defi¬ 
nition  by  the  original  describers,  MM.  Milne- Edwards  and  Haime, 
which  appeared  in  the  ‘  Annales  des  Sciences  Xaturelles’  in  1848, 1 
I  transcribe  in  full  their  own  words  : — 
“  Ce  genre  a  un  polypier  massif,  beaucoup  plus  dense  que  celui  des 
Stylocoenies.  Les  cloisons  sont  proportionnellement  epaisses,  et  on  ne 
distingue  jamais  a  bangle  des  calices  de  tubercules  columnaires. 
Enfin,  la  eolumelle  est  en  general  ties  peu  saillante.  Sous  tous  les 
autres  rapports,  les  Astrocoenies  ne  different  pas  du  genre  precedent 
[Stylocoenia]  ;  clles  se  separent  comme  lui  des  Stylines  par  les  calices 
polygonaux ;  des  Stephanocoenies,  par  l’absence  de  palis ;  des 
Phyllocoenies,  des  Dichocoenies  et  des  Heterocoenies  par  la  eolumelle 
styliforme.” 
After  a  few  words  relative  to  the  distribution  of  the  several 
species  constituting  the  genus,  the  same  authors  continue  : — “  Parmi 
celles  que  nous  avons  pu  etudier,  de  maniere  a  les  caracteriser 
sufffsamment,  les  unes  presentent  des  calices  eu  polygones  irreguliers 
et  de  grandeurs  un  peu  differentes,  parce  qu’elles  se  multiplient  a  la 
fois  par  bourgeonnement  lateral  et  par  bourgeonnement  marginal, 
tandis  que  d’autres  s’accroissent  seulement  en  surface  par  le 
premier  mode  de  bourgeonnement,  et  n’offrent  que  des  calices  de 
meme  grandeur  et  en  polygones  reguliers.” 
Two  years  later,  namely  in  1850,  the  same  authors  published  the 
first  part  of  their  great  work  on  British  Eossil  Corals,  Palaeont. 
Soc.  Monogr.,  at  p.  xxx.  of  which  is  a  definition  of  the  genus 
Astrocoenia  in  the  following  words  : — 
“  Corallum  very  dense  and  not  bearing  columnar  processes  as  in 
the  preceding  genus  [Stylocoenia].  Calices  polygonal.  Columella 
styliform,  not  projecting  much.  No  pali.  Septa  thick  ;  apparently 
eight  or  ten  systems,  two  or  four  of  the  secondary  septa  being 
as  much  developed  as  the  six  primary  ones.  Walls  thick  and  united, 
as  in  Stylocoenia.” 
It  is  not  a  little  remarkable  that  in  the  description  of  Astrocoenia 
> pulchella ,2  which  appears  in  the  same  volume  (p.  33)  and  is  of  the 
1  3eme  ser.  vol.  x.  p.  296. 
8  It  seems  probable  that  this  may  prove  to  be  generically  distinct  from  the 
Cretaceous  species. 
