Geological  Society.  75 
influence  of  unequal  temperature  or  friction  of  platinum  or  copper 
electrodes,  in  conducting  liquids  which  do  not  act  chemically  upon 
those  metals,  have  their  origin  in  temporary  changes  of  cohesion  of 
the  layers  of  metal  and  liquid  which  are  in  immediate  and  mutual 
contact,  and  may  be  considered  a  very  delicate  test  of  the  kind  and 
amount  of  temporary  molecular  movements  produced  by  those  causes. 
GEOLOGICAL  SOCIETY. 
[Continued  from  vol.  xlii.  p.  389.] 
June  7,  1871. — Joseph  Prestwich,  Esq.,  F.R.S.,  President, 
in  the  Chair. 
The  following  communications  were  read : — 
1.  "  On  the  persistence  of  Caryophyllia  cylindracea,  Reuss,  a 
Cretaceous  Coral,  in  the  Coral-fauna  of  the  Deep  Sea."  By  P. 
Martin  Duncan,  M.B.  Lond.,  F.R.S.,  F.G.S.,  Professor  of  Geology  in 
King's  College,  London. 
The  author  first  referred  to  the  synonyms  and  geological  distribu- 
tion of  Caryophyllia  cylindracea,  Reuss,  which  has  hitherto  been 
regarded  as  peculiar  to  the  White  Chalk,  and  as  necessarily  an  ex- 
tinct form,  inasmuch  as  it  belonged  to  a  group  possessing  only  fonr 
cycles  of  septa  in  six  systems,  one  of  the  systems  being  generally 
incomplete.  The  distribution  of  the  Caryvphyllioe,  of  this  group  in 
the  Gault  and  the  Upper  Chalk,  the  Miocene,  and  the  Pliocene  was 
noticed,  and  also  that  of  the  species  with  the  incomplete  cycle.  The 
falsity  of  this  generalization  was  shown  to  be  proved  by  the  results 
of  deep-sea  dredging  off  Havannah,  under  Count  Pourtales,  and 
off  the  Iberian  peninsula  under  Dr.  Carpenter  and  Mr.  Gwyn  Jef- 
freys. The  former  dredged  up  CaryophyUia  formosa  with  four 
complete  cycles ;  and  the  latter  obtained,  from  depths  between  690 
and  1090  fathoms,  a  group  of  forms  with  four  complete  and  incom- 
plete cycles.  This  group  had  a  Cretaceous  facies  ;  one  of  the  forms 
could  not  be  differentiated  from  Caryophyllia  cylindracea,  Reuss ; 
and  as  a  species  of  the  genus  Bathycyaihus  was  found  at  the  same 
time,  this  facies  was  rendered  more  striking.  The  representation  oi 
the  extinct  genera  Trochosmilia,  Parasmilia,  Synhelia,  and  Diblasus 
by  the  recent  Amphihelice,  Paracyathi,  and  Caryophylliai  was 
noticed ;  and  it  was  considered  that,  as  the  Cretaceous  forms  throve 
under  the  same  external  conditions,  some  of  them  only  being  per- 
sistent, there  must  be  some  law  which  determines  the  life-duration 
of  species  like  that  which  restricts  the  years  of  the  individual.  It 
was  shown  that  deep-sea  conditions  must  have  prevailed  within  the 
limits  of  the  diffusion  of  the  ova  of  coral  polyps  somewhere  on  the 
Atlantic  area  ever  since  the  Cretaceous  period. 
2.  "  Xote  on  an  Ichthyosaurus  (I.  entheJciodon)  from  Kimmeridge 
Bay,  Dorset."     By  J.  W.  Hulke,  Esq.,  F.R.S.,  F.G.S. 
In  this  paper  the  author  described  the  skeleton  of  an  Ichthyo- 
