﻿238 
  PROCEEDINGS 
  OF 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  [Mar. 
  23, 
  

  

  side-lobes 
  very 
  prominent, 
  punctate. 
  An 
  enormous 
  nuchal 
  spine. 
  

   Body-rings 
  4. 
  Tail 
  equal 
  to 
  the 
  head, 
  with 
  a 
  strong 
  7-ringed 
  axis 
  

   and 
  smooth 
  punctate 
  sides, 
  margin 
  distinct. 
  

  

  Leperditia 
  Solvensis, 
  Jones, 
  Ann. 
  & 
  Mag. 
  Nat. 
  Hist. 
  2nd 
  ser. 
  vol. 
  xvii. 
  

   Feb. 
  1856, 
  p. 
  95. 
  pi. 
  7. 
  fig. 
  16. 
  

  

  This 
  curious 
  little 
  bivalved 
  Crustacean 
  was 
  formerly 
  thought 
  to 
  

   belong 
  to 
  the 
  Llandeilo 
  formation 
  of 
  Wales 
  ; 
  but 
  the 
  beds 
  at 
  Solva 
  

   are 
  now 
  proved 
  to 
  belong 
  to 
  the 
  Lingula-nags. 
  We 
  must 
  add, 
  

   therefore, 
  the 
  bivalve 
  Phyllopods 
  to 
  the 
  older 
  fauna. 
  

  

  Locality, 
  Solva 
  Harbour, 
  west 
  side, 
  in 
  Lingula-nags. 
  

  

  Theca 
  corrtjgata, 
  spec. 
  nov. 
  PL 
  XIII. 
  fig. 
  10. 
  

  

  The 
  characters 
  of 
  this 
  small 
  species 
  reside 
  in 
  the 
  strong 
  rugose 
  lines 
  

   of 
  growth. 
  Except 
  in 
  these, 
  it 
  is 
  not 
  unlike 
  some 
  of 
  the 
  species 
  of 
  the 
  

   Tremadoc 
  slate. 
  It 
  is 
  quite 
  distinct 
  from 
  any 
  published 
  form. 
  

  

  Locality, 
  Porth-y-Rhaw, 
  abundant 
  in 
  lower 
  beds. 
  

  

  Protospongia 
  fekestrata, 
  gen. 
  et 
  spec. 
  nov. 
  PI. 
  XIII. 
  fig. 
  12. 
  

  

  The 
  Sponge 
  which 
  is 
  here 
  introduced 
  to 
  notice 
  is 
  remarkable 
  for 
  

   the 
  size 
  of 
  the 
  spiculse, 
  which 
  however 
  do 
  not 
  exceed 
  in 
  magnitude 
  

   those 
  of 
  the 
  Astrceospongia 
  of 
  Ferd. 
  Roemer 
  — 
  a 
  sponge 
  figured 
  by 
  that 
  

   author 
  in 
  his 
  work 
  on 
  the 
  Upper 
  Silurian 
  Fossils 
  of 
  Western 
  Ten- 
  

   nessee, 
  pi. 
  1. 
  fig. 
  6. 
  

  

  Nor 
  do 
  they 
  much 
  exceed 
  in 
  size 
  those 
  described, 
  but 
  not 
  figured, 
  

   by 
  Prof. 
  McCoy 
  in 
  his 
  ' 
  Synopsis 
  of 
  the 
  Silurian 
  Fossils 
  of 
  Ireland/ 
  

   p. 
  67. 
  The 
  specimen 
  so 
  described 
  is 
  in 
  Sir 
  R. 
  Griffith's 
  cabinet, 
  and 
  is 
  

   well 
  worth 
  the 
  study 
  of 
  the 
  naturalist. 
  The 
  spicule 
  are 
  even 
  larger 
  

   than 
  those 
  of 
  our 
  fossil, 
  and 
  have 
  six 
  rays 
  (Acantliospongia 
  is 
  the 
  

   name 
  bestowed 
  by 
  McCoy), 
  while 
  ours 
  have, 
  to 
  all 
  appearance, 
  only 
  

   quadrate 
  spiculae, 
  and 
  all 
  on 
  one 
  plane, 
  that 
  of 
  the 
  general 
  exterior 
  

   surface. 
  

  

  Gen. 
  Char. 
  — 
  General 
  form? 
  The 
  skeleton 
  is 
  loosely 
  reticular, 
  

   formed 
  of 
  very 
  large 
  cruciform 
  spiculae, 
  the 
  branches 
  of 
  which 
  cross 
  

   each 
  other 
  at 
  an 
  angle 
  of 
  80°, 
  and 
  only 
  in 
  one 
  plane, 
  no 
  ascending 
  or 
  

   descending 
  branches 
  rising 
  from 
  the 
  point 
  of 
  conjunction. 
  

  

  The 
  skeleton 
  thus 
  constituted 
  is 
  far 
  from 
  being 
  uniform. 
  Some 
  

   of 
  the 
  branches 
  are 
  double 
  or 
  treble 
  the 
  size 
  of 
  the 
  others, 
  appearing 
  

   as 
  if 
  three 
  or 
  more 
  spiculse 
  had 
  become 
  connate. 
  The 
  larger 
  branches 
  

   maintain 
  the 
  same 
  angles 
  as 
  the 
  smaller, 
  the 
  latter 
  filling 
  in, 
  as 
  it 
  

   were, 
  the 
  interstices 
  between 
  the 
  larger, 
  which 
  are 
  very 
  slightly 
  

   tapering, 
  and 
  often 
  measure 
  nearly 
  \ 
  inch 
  in 
  length. 
  The 
  smaller 
  

   branches 
  vary 
  from 
  one 
  to 
  two 
  lines 
  or 
  less 
  in 
  length. 
  The 
  angles 
  

   occasionally 
  vary, 
  but 
  not 
  much 
  so 
  ; 
  in 
  our 
  figure 
  they 
  are 
  more 
  

   rectangular 
  than 
  usual. 
  

  

  The 
  only 
  Silurian 
  Sponges 
  with 
  which 
  I 
  am 
  acquainted 
  in 
  Britain, 
  

   which 
  show 
  decided 
  spiculse, 
  are 
  those 
  above 
  mentioned, 
  and 
  the 
  

   Amphispongia, 
  a 
  form 
  resembling 
  Grantia, 
  and 
  described 
  by 
  myself 
  *, 
  

   from 
  the 
  Pentland 
  Hills. 
  These 
  have 
  both 
  of 
  them 
  spiculse 
  in 
  

  

  * 
  Mem. 
  Geol. 
  Surv., 
  Explanation 
  of 
  Edinburgh 
  Sheet. 
  &c. 
  pi. 
  2. 
  fig. 
  3. 
  

  

  