﻿806 
  Forty-seventh 
  Report 
  on 
  the 
  State 
  Museum. 
  

  

  vaulted 
  muscular 
  platform 
  (see 
  Part 
  1, 
  pp. 
  46, 
  165) 
  is 
  confirmed 
  

   by 
  evidence 
  which 
  is 
  unusually 
  complete 
  and 
  conclusive. 
  Various 
  

   intermediate 
  stages 
  have 
  also 
  been 
  indicated 
  by 
  which 
  a 
  similar 
  

   resultant 
  is 
  attained 
  from 
  the 
  primitive 
  obolelloids 
  through 
  

   Lakhmina, 
  Elkania 
  and 
  Dinobolus 
  (p. 
  28, 
  plate 
  iii, 
  ivb). 
  The 
  

   chronogeny 
  of 
  the 
  various 
  elements 
  is 
  in 
  full 
  accord 
  with 
  the 
  

   structural 
  progress 
  along 
  both 
  lines 
  of 
  derivation 
  ; 
  a 
  single 
  genus 
  

   in 
  this 
  series, 
  Lingulops, 
  enduring 
  in 
  an 
  unmodified 
  condition 
  

   from 
  faunas 
  (Hudson 
  river) 
  antedating 
  the 
  appearance 
  of 
  Trimer- 
  

   ella, 
  to 
  those 
  in 
  which 
  Trimerella 
  abounds 
  (Magara 
  and 
  Guelph 
  

   dolomites). 
  » 
  

  

  The 
  entire 
  group 
  of 
  linguloid 
  and 
  oboloid 
  genera 
  is 
  bound 
  

   together, 
  as 
  already 
  shown, 
  by 
  the 
  possession 
  of 
  an 
  uninclosed 
  

   marginal 
  pedicle. 
  They 
  compose 
  the 
  Mesocaulia 
  or 
  Lingulacea 
  

   of 
  Waagen 
  (1883) 
  (Atremata 
  of 
  Beecher, 
  1891).* 
  

  

  The 
  leading 
  element 
  in 
  this 
  group, 
  Ltngula, 
  attained 
  a 
  static 
  

   condition 
  in 
  early 
  Silurian 
  faunas 
  ; 
  the 
  oscillations 
  of 
  the 
  type 
  

   were 
  mainly 
  confined 
  to 
  the 
  preceding 
  faunas; 
  those 
  of 
  later 
  

   date 
  are 
  but 
  slight 
  departures 
  in 
  a 
  few 
  directions 
  only. 
  The 
  

   combination 
  termed 
  Lij^gula 
  having 
  once 
  become 
  fixed, 
  main- 
  

   tained 
  it 
  self 
  with 
  unexampled 
  adjustment 
  to 
  changing 
  conditions, 
  

   even 
  into 
  the 
  existing 
  seas. 
  Glossina, 
  Dignomia, 
  Barroisella 
  

   and 
  Tomasina, 
  which 
  represent 
  early 
  deviations 
  along 
  the 
  line 
  of 
  

   its 
  descent, 
  embody 
  no 
  substantial 
  variations, 
  though 
  the 
  two 
  

   last 
  named 
  demonstrate 
  the 
  gradual 
  assumption 
  of 
  articulating 
  

   processes, 
  a 
  tendency 
  which 
  not 
  infrequently 
  makes 
  itself 
  appa- 
  

   rent 
  in 
  this 
  group 
  where 
  the 
  pedicle-passage 
  is 
  wholly 
  marginal. 
  

   It 
  is 
  seen 
  in 
  Spondylobolus, 
  is 
  sometimes 
  faintly 
  manifested 
  in 
  

   Obolus 
  and 
  Obolella; 
  in 
  Trimerella 
  there 
  is 
  occasionally 
  a 
  low 
  

   cardinal 
  process, 
  as 
  shown 
  by 
  Davidson 
  and 
  King, 
  and 
  Gotland 
  

   specimens 
  of 
  T. 
  Lindstrcemi 
  bear 
  long 
  submargiual 
  slotted 
  ridges 
  

  

  * 
  To 
  insure 
  greater 
  freedom 
  of 
  treatment 
  and 
  relief 
  from 
  the 
  embarrassments 
  of 
  an 
  inelastic 
  

   classification, 
  the 
  discussions 
  in 
  these 
  volumes 
  have 
  intentionally 
  been 
  left 
  free 
  of 
  terms 
  desig- 
  

   nating 
  taxonomic 
  values 
  higher 
  than 
  genera. 
  By 
  provisionally 
  declining 
  allegiance 
  to 
  any 
  pre- 
  

   scribed 
  formulas 
  n 
  classification, 
  not 
  only 
  has 
  the 
  manner 
  of 
  treatment 
  of 
  the 
  comprehensive 
  

   material 
  studied 
  bsen 
  more 
  natural, 
  but 
  the 
  student 
  will 
  find 
  him 
  elf 
  less 
  encumbered 
  with 
  

   artificial 
  r 
  -strictions 
  and 
  freer 
  from 
  collisions 
  with 
  rock-ribbed 
  party-walls, 
  which, 
  to 
  use 
  an 
  

   old 
  Scotch 
  phrase, 
  "are 
  nane 
  o' 
  God's 
  makinV 
  It 
  had, 
  nevertheless, 
  been 
  the 
  intention 
  to 
  

   h 
  i'ii 
  narize, 
  in 
  a 
  tabulated 
  form, 
  at 
  the 
  close 
  of 
  this 
  work, 
  the 
  broader 
  relations 
  of 
  the 
  genera 
  

   discussed, 
  not 
  with 
  any 
  intention 
  of 
  introducing 
  a 
  series 
  of 
  new 
  taxonomic 
  terms, 
  but 
  to 
  

   express 
  succinctly 
  the«ie 
  interrelations 
  as 
  they 
  appear 
  upon 
  a 
  review 
  of 
  the 
  whole 
  field 
  of 
  

   research. 
  Such 
  a 
  table 
  will 
  be 
  found 
  at^the 
  close 
  of 
  this 
  chapter. 
  

  

  