﻿Yol. 
  53.] 
  PATINA 
  OF 
  THE 
  KE1SLEY 
  I/OIISTONE. 
  73 
  

  

  But 
  the 
  distribution 
  and 
  furcation 
  of 
  the 
  ribs 
  are 
  shown 
  by 
  the 
  

   figures 
  of 
  these 
  American 
  species 
  to 
  be 
  slightly 
  different. 
  

  

  Camebella 
  ? 
  Thomsoni 
  (Davidson). 
  

  

  This 
  species, 
  which 
  Davidson 
  l 
  doubtfully 
  put 
  in 
  the 
  genus 
  

   Bhynclionella, 
  resembles 
  in 
  external 
  characters 
  Billings's 
  Camerella 
  

   Yolborthi 
  2 
  from 
  the 
  Black 
  River 
  Limestone 
  of 
  Canada 
  and 
  Torn- 
  

   quist's 
  Camerella 
  angulosa 
  3 
  from 
  the 
  Leptama-Limestone. 
  I 
  think, 
  

   therefore, 
  that 
  it 
  is 
  safer 
  to 
  assign 
  it 
  to 
  the 
  genus 
  Camerella 
  than 
  

   to 
  BhyncJionella, 
  used 
  in 
  its 
  old 
  wide 
  sense. 
  

  

  Davidson 
  gives 
  only 
  Craighead 
  Quarry 
  and 
  Penwhapple 
  Glen 
  as 
  

   the 
  localities 
  in 
  which 
  this 
  species 
  has 
  previously 
  been 
  found. 
  

  

  Synteophia 
  appixis, 
  sp. 
  n. 
  (PI. 
  VI. 
  figs. 
  4 
  & 
  4 
  a.) 
  

  

  Hall 
  & 
  Clarke 
  i 
  have 
  recently 
  established 
  the 
  new 
  genus 
  

   SyntropJiia 
  for 
  a 
  small 
  group 
  of 
  brachiopods 
  which 
  externally 
  

   resemble 
  Billingsella 
  and 
  Protorthis, 
  but 
  in 
  their 
  internal 
  structure 
  

   are 
  related 
  to 
  the 
  genus 
  StricJclandinia 
  of 
  a 
  later 
  date. 
  A 
  single 
  

   pedicle-valve 
  of 
  a 
  species 
  of 
  this 
  genus 
  Sy 
  atrophia 
  from 
  the 
  Keisley 
  

   Limestone 
  is 
  in 
  the 
  Woodwardian 
  Museum, 
  bearing 
  a 
  close 
  resem- 
  

   blance 
  to 
  Whitfield's 
  species 
  JSyn. 
  lateralis, 
  from 
  the 
  Calciferous 
  

   formation 
  of 
  America. 
  Our 
  specimen 
  is 
  transversely 
  elongate, 
  

   strongly 
  convex, 
  with 
  a 
  straight 
  hinge-line 
  nearly 
  equal 
  to 
  the 
  

   greatest 
  width 
  of 
  the 
  shell. 
  The 
  valve 
  is 
  divided 
  into 
  two 
  rounded 
  

   convex 
  lobes 
  by 
  a 
  smooth 
  sinus 
  commencing 
  a 
  short 
  distance 
  in 
  

   front 
  of 
  the 
  umbo, 
  and 
  extending 
  with 
  increasing 
  width 
  to 
  the 
  

   anterior 
  margin, 
  which 
  it 
  gently 
  sinuates. 
  The 
  umbo 
  is 
  small, 
  not 
  

   prominent, 
  but 
  incurved 
  over 
  the 
  hinge-line. 
  At 
  the 
  cardinal- 
  

   lateral 
  angles 
  there 
  is 
  a 
  slight 
  flattening 
  of 
  the 
  convexity 
  of 
  the 
  

   lobes 
  of 
  the 
  valve 
  in 
  the 
  vicinity 
  of 
  the 
  hinge-line. 
  The 
  surface 
  of 
  

   the 
  valve 
  is 
  smooth, 
  except 
  for 
  a 
  few 
  concentric 
  striae, 
  of 
  which 
  the 
  

   marginal 
  ones 
  are 
  more 
  strongly 
  incised 
  than 
  the 
  others. 
  

  

  As 
  to 
  the 
  internal 
  structure 
  of 
  the 
  valve, 
  the 
  median 
  septum 
  is 
  

   seen 
  through 
  the 
  thin 
  shell 
  to 
  extend 
  forward 
  from 
  the 
  beak 
  for 
  

   about 
  two-thirds 
  the 
  length 
  of 
  the 
  shell, 
  but 
  the 
  spondylium 
  

   formed 
  by 
  the 
  dental 
  plates 
  is 
  not 
  visible. 
  

  

  The 
  points 
  in 
  which 
  our 
  species 
  differs 
  from 
  Syn. 
  lateralis 
  

   ("Whitf 
  .) 
  are 
  the 
  inferior 
  height 
  and 
  prominence 
  of 
  the 
  umbo, 
  and 
  the 
  

   more 
  clearly 
  defined 
  and 
  rounded 
  median 
  sinus. 
  

  

  millim. 
  

  

  Length 
  of 
  shell 
  3 
  

  

  Breadth 
  5 
  

  

  RHYNCHOTEEMA 
  cf. 
  EEXTATUM, 
  Hall. 
  

  

  The 
  species 
  Eh. 
  dentatum 
  occurs 
  in 
  the 
  Trenton 
  Limestone 
  of 
  

  

  1 
  'Mon. 
  Brit. 
  Foss. 
  Brach.,' 
  vol. 
  iii. 
  (1864-71) 
  p. 
  186, 
  pi. 
  xxiv. 
  fig. 
  18. 
  

  

  2 
  ' 
  Canadian 
  Naturalist 
  & 
  Geologist,' 
  vol. 
  iv. 
  (1859) 
  pp. 
  301, 
  302 
  & 
  445, 
  

   figs. 
  23, 
  24. 
  

  

  3 
  ' 
  Om 
  Lagerfolj. 
  i 
  Dal. 
  undersilur 
  Bildn.,' 
  Lunds 
  Universitets 
  Arsskrift, 
  

   vol. 
  iii. 
  (1866) 
  p. 
  17 
  ; 
  Lindstrora, 
  'Fragm. 
  Silur.' 
  (1880) 
  p. 
  23, 
  pi. 
  xiii. 
  figs. 
  14-19. 
  

  

  * 
  ■ 
  Pal. 
  N. 
  Y.,' 
  vol. 
  viii. 
  Brach. 
  pt. 
  ii. 
  (1894) 
  p. 
  216, 
  pi. 
  lxii. 
  figs. 
  1-10. 
  

  

  