Mr.  G.  Maw  on  the  Geology  of  the  Plain  of  Morocco.       315 
nature  of  the  under  lip  in  Limidus  differs  from  that  prevailing 
among  the  Crustacea.  Dr.  Dohrn  also  recognizes  the  relationship 
of  the  Merostoniata  to  the  Trilobites,  as  shown  especially  by  the 
development  of  Limulus.  and  considers  that  the  three  forms  (Limu- 
Jidce,  Eurifpteridcr,  and  Trihbita)  should  be  combiued  in  one  group 
under  the  name  of  Giyantostraca,  proposed  by  Hiickel,  and  placed 
beside  the  Crustacea.  The  author  stated,  on  the  authority  of  Prof. 
Owen,  that  Limulus  really  possesses  two  pairs  of  appendages  which 
receive  their  nerves  from  the  supracesophageal  ganglion,  that, 
according  to  Dr.  Packard,  the  young  Limidus  passes  through  a 
Xauplius-stage  while  in  the  egg,  that  no  argument  could  be 
founded  upon  the  lower  lip,  the  condition  of  which  varied  extremely 
in  the  three  groups  proposed  to  be  removed  from  the  Crustacea ;  and 
he  main  Laired  that,  even  from  the  ultra-Darwinian  point  of  view 
taken  bv  Dr.  Dohrn,  the  adoption  of  his  proposal  would  be  fatal  to 
the  application  of  the  hypothesis  of  evolution  to  the  class  Crustacea. 
January  10,  1872. — Joseph  Prestwich,  Esq.,  F.R.S.,  President, 
in  the  Chair. 
The  following  communications  were  read : — 
1.  '•  On  C>[closti</ma,  Lepidodendron,  and  Knorria  from  Xil- 
torkan."     By  Prof.  Oswald  Heer,  F.C.G.S. 
In  this  paper  the  author  indicated  the  characters  of  certain  fossils 
from  the  Yellow  Sandstone  of. the  South  of  Ireland,  referred  by  him 
to  the  above  genera,  and  mentioned  in  his  paper  "  On  the  Carboni- 
ferous Flora  of  Bear  Island/*'  read  before  the  Society  on  Xovember  9, 
1870  (see  Q.  J.  G.  S.  vol.  xxvii.  p.  1).  He  distinguished  as  species 
Cyelostiyma  IcUtorlcense,  Haught.,  C.  minutum  (Haught.),  Knorria 
acfcidariSf  Gopp.,  var.  Bailyana,  and  Lepidodendron  VeltJieimianum, 
Sternb. 
2.  "  Xotes  on  the  Geology  of  the  Plain  of  Marocco,  and  the  Great 
Atlas."     By  George  Maw,  Esq.,  F.G.S.  &c. 
The  author  described  first  the  characters  presented  by  the  coast  of 
Marocco,  and  then  the  phenomena  observed  by  him  in  his  progress 
into  the  interior  of  the  country  and  in  the  Atlas  Chain.  The  oldest 
rocks  observed  were  ranges  of  metamorphic  rocks  bounding  the 
plain  of  Marocco,  intcrbedded  porphyrites  and  the  porphyritic  tuffs 
forming  the  backbone  of  the  Atlas  Chain,  and  the  Mica-schists  of 
Djeb  Tezah  in  the  Atlas.  At  many  points  in  the  lateral  valleys  of 
the  Atlas  almost  vertical  grey  shales  were  crossed ;  the  age  of  these 
was  unknown.  Above  these  comes  a  Red  Sandstone  and  Limestone 
series,  believed  to  be  of  Cretaceous  age,  and  beds  possibly  of  Miocene 
age,  which  occupied  the  valleys  of  the  Atlas  and  covered  the  plain 
of  Marocco,  where  vestiges  of  them  remain  in  the  form  of  tubular 
hills.  The  probable  age  of  these  beds  was  determined  on  the  evidence 
of  fossils.  The  author  noticed  the  sequence  of  denuding  and  eruptive 
phenomena  by  which  the  arrangement  and  distribution  of  these 
rocks  has  been  modified,  and  described  the  more  recent  changes — 
resulting  in  the  formation  of  enormous  boulder-beds  flanking  the 
