﻿Vol. 
  53.] 
  FOSSILS 
  FKOM 
  THE 
  MORTE 
  SLATES, 
  ETC. 
  451 
  

  

  Rhyncho^ella 
  hercxnica, 
  Kayser? 
  (PL 
  XXXIY. 
  figs. 
  4, 
  4«, 
  

   46 
  & 
  5.) 
  

  

  Locality. 
  Oakhampton. 
  Four 
  specimens. 
  

  

  Size. 
  Probably 
  about 
  14 
  mm. 
  in 
  width 
  and 
  length, 
  and 
  7 
  mm. 
  in 
  

   depth. 
  

  

  Description. 
  Shell 
  suborbicular, 
  rather 
  flattened. 
  Umbo 
  rather 
  

   elevated, 
  incurved. 
  Area 
  large, 
  slightly 
  concave, 
  with 
  defined 
  

   edges. 
  Dental 
  lamellae 
  strong. 
  Fold 
  and 
  sinus 
  low, 
  wide, 
  

   probably 
  arching. 
  Ribs 
  strong, 
  numerous, 
  reaching 
  to 
  the 
  umbo, 
  

   transversely 
  plaited, 
  numbering 
  about 
  7 
  on 
  the 
  fold, 
  6 
  on 
  the 
  sinus, 
  

   and 
  8 
  or 
  9 
  on 
  each 
  side. 
  

  

  This 
  seems 
  to 
  belong 
  to 
  the 
  group 
  of 
  Rh. 
  pleurodon, 
  but 
  differs 
  

   from 
  the 
  Upper 
  Devonian 
  members 
  of 
  that 
  group 
  in 
  the 
  much 
  greater 
  

   number 
  of 
  ribs 
  on 
  its 
  fold. 
  In 
  that 
  respect 
  it 
  approaches 
  Rh. 
  llanclo- 
  

   veriana, 
  Davidson, 
  1 
  but 
  its 
  dental 
  lamella? 
  are 
  placed 
  much 
  nearer 
  

   together, 
  and 
  it 
  does 
  not 
  seem 
  to 
  have 
  the 
  serrations, 
  described 
  by 
  

   Davidson, 
  on 
  that 
  shell. 
  None 
  of 
  Schnur's 
  species 
  approach 
  it. 
  

  

  In 
  its 
  crushed 
  condition 
  the 
  shape 
  of 
  its 
  fold 
  is 
  obscured, 
  but 
  if, 
  

   as 
  seems 
  possible, 
  it 
  was 
  gently 
  arched, 
  it 
  might 
  be 
  referred 
  to 
  

   the 
  Lower 
  Devonian 
  Rh. 
  hercynica, 
  Kayser, 
  2 
  which, 
  in 
  the 
  number 
  

   of 
  ribs 
  and 
  other 
  characters, 
  it 
  seems 
  to 
  approach. 
  

  

  Rhynchonella 
  nympha, 
  Barrande 
  ? 
  (PI. 
  XXXIY. 
  figs. 
  6 
  & 
  7.) 
  

  

  Locality. 
  Oakhampton 
  Quarry. 
  Three 
  specimens. 
  

  

  Size. 
  Apparently 
  something 
  like 
  25 
  mm. 
  wide 
  by 
  20 
  mm. 
  

   high. 
  

  

  This 
  form 
  seems 
  distinguished 
  from 
  the 
  preceding 
  by 
  its 
  larger 
  

   size, 
  by 
  its 
  fewer 
  and 
  stronger 
  ribs, 
  and 
  by 
  its 
  more 
  extended 
  sinus 
  

   bearing 
  fewer 
  ribs. 
  It 
  appears 
  to 
  be 
  common, 
  but 
  in 
  Dr. 
  Hicks's 
  

   collection 
  is 
  represented 
  only 
  by 
  very 
  fragmental 
  specimens. 
  

  

  Its 
  fold 
  appears 
  to 
  have 
  been 
  somewhat 
  elevated, 
  flattened, 
  and 
  

   considerably 
  extended 
  in 
  front, 
  and 
  to 
  have 
  borne 
  either 
  5 
  or 
  6 
  

   strong 
  ribs, 
  while 
  there 
  were 
  probably 
  about 
  7 
  smaller 
  ribs 
  on 
  each 
  

   side. 
  The 
  ribs 
  are 
  very 
  acute 
  and 
  elevated, 
  extend 
  quite 
  over 
  the 
  

   umbo, 
  and 
  sharply 
  interlock 
  at 
  the 
  margins. 
  

  

  So 
  far 
  as 
  can 
  be 
  seen 
  in 
  their 
  defective 
  state, 
  our 
  specimens 
  

   accurately 
  agree 
  with 
  the 
  figures 
  of 
  Rh. 
  nympha, 
  Barrande, 
  3 
  given 
  

   by 
  Kayser 
  [from 
  Lower 
  Devonian 
  shells]. 
  4 
  While 
  from 
  their 
  

   evidence 
  it 
  cannot 
  be 
  said 
  to 
  be 
  identical, 
  so 
  far 
  as 
  that 
  evidence 
  

   goes 
  it 
  is 
  indistinguishable 
  from 
  them. 
  

  

  1 
  1869. 
  Davidson, 
  ' 
  Brit. 
  Foss. 
  Brach.' 
  vol! 
  iii. 
  p. 
  184 
  & 
  pi. 
  xxiv. 
  figs. 
  8-13. 
  

  

  2 
  1878. 
  Kayser, 
  Abh. 
  geol. 
  Specialk. 
  Preuss. 
  vol. 
  ii. 
  pt. 
  iv. 
  p. 
  153 
  & 
  pi. 
  xxv. 
  

   figs. 
  9-11. 
  

  

  3 
  1847. 
  Barrande, 
  ' 
  Naturw. 
  Abhandi.' 
  vol. 
  i. 
  p. 
  422 
  & 
  pi. 
  xx. 
  figs. 
  6-8 
  ; 
  and 
  

   1879. 
  Barrande, 
  ' 
  Syst. 
  Sil. 
  Boheme,' 
  vol. 
  v. 
  pi. 
  xxix. 
  figs. 
  10-18, 
  etc., 
  Etage 
  F. 
  

  

  4 
  1878. 
  Kayser, 
  Abh. 
  geol. 
  Specialk. 
  Preuss. 
  vol. 
  ii. 
  pt. 
  iv. 
  p. 
  142 
  & 
  pis. 
  xxv. 
  

   L 
  figs. 
  1, 
  2, 
  6-11, 
  xxvi. 
  figs. 
  15-18. 
  

  

  2h2 
  

  

  