﻿Report 
  of 
  the 
  State 
  Geologist. 
  805 
  

  

  Such 
  an 
  inceptive 
  form 
  would 
  presumptively 
  be 
  wholly 
  elemen- 
  

   tary 
  in 
  its 
  contour, 
  outline 
  and 
  structure 
  of 
  pedicle- 
  opening, 
  and, 
  

   in 
  fact, 
  be 
  little 
  more 
  than 
  an 
  amplification 
  of 
  the 
  infantile 
  con- 
  

   dition 
  in 
  its 
  descendants. 
  It 
  has 
  since 
  been 
  observed 
  by 
  Beecher 
  

   that 
  the 
  embryonic 
  shell 
  or 
  protoconch 
  (protegulum) 
  of 
  the 
  

   brachiopod 
  is 
  " 
  semicircular 
  or 
  semielliptical 
  in 
  outline, 
  with 
  a 
  

   straight 
  or 
  arcuate 
  hinge-line, 
  and 
  no 
  hinge-area. 
  A 
  slight 
  pos- 
  

   terior 
  gaping 
  is 
  produced 
  by 
  the 
  pedicle- 
  valve 
  being 
  usually 
  more 
  

   convex 
  than 
  the 
  brachial."* 
  It 
  appears, 
  furthermore, 
  to 
  be 
  

   composed 
  of 
  corneous, 
  impunctate 
  shell-tissue. 
  The 
  same 
  

   investigator 
  finds 
  that 
  the 
  species 
  described 
  by 
  Billings 
  as 
  

   Obolus 
  Labradtricus, 
  from 
  a 
  horizon 
  at 
  L'Anse 
  au 
  Loup, 
  now 
  

   regarded 
  as 
  Lower 
  Cambrian, 
  and 
  subsequently 
  identified 
  by 
  

   "Walcott, 
  at 
  the 
  same 
  horizon 
  at 
  Swanton, 
  Yermont,f 
  is 
  the 
  

   nearest 
  approach 
  of 
  the 
  adult 
  brachiopod 
  to 
  the 
  simple 
  type 
  of 
  

   the 
  protoconch 
  ; 
  a 
  semicircular 
  corneous 
  shell, 
  with 
  gaping 
  car- 
  

   dinal 
  margins. 
  This 
  shell 
  has 
  been 
  distinguished 
  by 
  the 
  generic 
  

   term 
  Paterina. 
  

  

  There 
  are, 
  undoubtedly, 
  other 
  brachiopodous 
  shells 
  of 
  obolelloid 
  

   type 
  that 
  are 
  quite 
  as 
  ancient 
  as 
  Paterixa 
  ; 
  still 
  the 
  latter 
  exem- 
  

   plifies 
  the 
  line 
  along 
  which 
  the 
  development 
  of 
  more 
  complicated 
  

   forms 
  has 
  proceeded, 
  and 
  it 
  is 
  in 
  all 
  respects 
  the 
  simplest 
  known 
  

   brachiopod. 
  Paterina 
  is 
  an 
  embodiment 
  of 
  the 
  predicted 
  ances- 
  

   tor 
  of 
  the 
  linguloids 
  and 
  obolelloid 
  s, 
  and, 
  with 
  our 
  present 
  knowl- 
  

   edge, 
  it 
  appears 
  to 
  be 
  the 
  radicle 
  of 
  all 
  the 
  Brachiopoda, 
  both 
  

   inarticulate 
  and 
  articulate. 
  

  

  The 
  departure 
  from 
  Llngula, 
  through 
  Lingulops 
  and 
  Lingu- 
  

   las2>ia 
  to 
  Trimerella, 
  by 
  the 
  progressive 
  development 
  of 
  the 
  

  

  * 
  Beecher; 
  Development 
  of. 
  the 
  Brachiopoda, 
  Part 
  I, 
  Introduction; 
  American 
  Journal 
  of 
  

   Science, 
  vol. 
  XLI, 
  p. 
  344. 
  1891. 
  

  

  t 
  In 
  a 
  later 
  work 
  Mr. 
  Walcott 
  has 
  concluded 
  that 
  the 
  Swanton 
  fossil 
  is 
  sufficiently 
  distinct 
  

   from 
  the 
  typical 
  Obolus 
  (or 
  Kutorgind) 
  Labradoricus 
  to 
  require 
  a 
  new 
  designation, 
  and 
  has 
  

   therefore 
  termed 
  it 
  Kutorgina 
  Labradorica, 
  var. 
  Sioantonensis 
  CSee 
  "Fauna 
  of 
  the 
  Lower 
  

   Cambrian; 
  " 
  Tenth 
  Ann 
  Rept. 
  Director 
  U. 
  S 
  Geological 
  Survey, 
  pi. 
  lxiv, 
  figs. 
  2, 
  3, 
  dated 
  1890, 
  

   issued 
  1*90- 
  The 
  figures 
  given 
  in 
  the 
  work 
  cited 
  show 
  that 
  the 
  var. 
  Sioantonensis 
  is 
  in 
  many 
  

   respects 
  the 
  more 
  primitive 
  type, 
  its 
  valves 
  being 
  the 
  more 
  nearly 
  equiconvex, 
  its 
  surface 
  

   characters 
  simple 
  concentric 
  striae, 
  while 
  in 
  the 
  typical 
  0. 
  Labradoricus, 
  there 
  is 
  a 
  conspicuous 
  

   elevation 
  of 
  the 
  umbo 
  of 
  the 
  pedicle-valve, 
  a 
  low 
  median 
  sinus 
  on 
  the 
  brachial 
  valve, 
  as 
  well 
  as 
  

   indications 
  of 
  radial 
  plications 
  about 
  the 
  beak; 
  all 
  these 
  are 
  secondary 
  characters 
  which 
  indi 
  

   cate 
  progress 
  toward 
  the 
  true 
  Kutorgisa 
  (K. 
  cingulata). 
  It 
  seems 
  evident 
  that 
  the 
  generic 
  

   term 
  Patercsa 
  was 
  based 
  upon 
  the 
  Swanton 
  fossil, 
  and 
  hence, 
  if 
  the 
  author's 
  intentions 
  are 
  

   correctly 
  interpreted, 
  the 
  type 
  of 
  the 
  genus 
  is 
  Pater 
  ina 
  Sioantonensis, 
  Walcott. 
  As 
  to 
  the 
  

   value 
  to 
  be 
  ascribed 
  to 
  differences 
  of 
  shell-composition 
  within 
  a 
  given 
  association 
  of 
  closely 
  

   related 
  genera, 
  see 
  remarks 
  under 
  the 
  discussion 
  of 
  Lingttla 
  and 
  Trimerella 
  and 
  in 
  the 
  fol- 
  

   i 
  owing 
  pages. 
  

  

  