﻿Report 
  of 
  the 
  State 
  Geologist. 
  901 
  

  

  " 
  Here 
  we 
  find 
  nineteen 
  species, 
  the 
  majority 
  of 
  which 
  have 
  been 
  

   described 
  by 
  Prof. 
  Hall 
  under 
  Fenestella. 
  Seven 
  more 
  species 
  

   are 
  described 
  by 
  that 
  author 
  from 
  the 
  Hamilton 
  group.* 
  

  

  "Above 
  this 
  horizon 
  the 
  genus 
  is 
  not 
  known." 
  

  

  To 
  me 
  it 
  seems 
  scarcely 
  credible 
  that 
  Mr. 
  Prout, 
  who 
  had 
  

   described 
  several 
  species 
  of 
  Fenestella 
  and 
  who 
  had 
  proposed 
  

   two 
  new 
  genera 
  of 
  Fenestellidae, 
  and 
  who 
  in 
  his 
  descriptions 
  and 
  

   remarks 
  showed 
  that 
  he 
  understood 
  the 
  subject, 
  should 
  be 
  so 
  

   greatly 
  at 
  fault 
  in 
  describing 
  a 
  form 
  which 
  differed 
  from 
  others 
  

   which 
  he 
  had 
  described 
  only 
  in 
  having 
  a 
  prominent 
  keel 
  or 
  

   carina 
  expanded 
  at 
  the 
  summit, 
  especially 
  as 
  in 
  his 
  descriptions 
  

   he 
  almost 
  invariably 
  describes 
  the 
  keel, 
  its 
  height 
  and 
  general 
  

   appearance. 
  

  

  After 
  carefully 
  reading 
  his 
  description 
  and 
  examining 
  the 
  

   illustrations, 
  which 
  are 
  of 
  much 
  more 
  importance, 
  I 
  am 
  fully 
  

   satisfied 
  that 
  he 
  had 
  before 
  him 
  some 
  form 
  of 
  Unitrypa, 
  evidently 
  

   the 
  first 
  that 
  he 
  had 
  seen, 
  and 
  the 
  characters 
  of 
  which, 
  in 
  the 
  

   poor 
  condition 
  of 
  the 
  only 
  specimen 
  observed 
  by 
  him, 
  might 
  

   easily 
  be 
  misleading 
  to 
  him. 
  

  

  Admitting 
  Mr. 
  Prout 
  to 
  have 
  been 
  describing 
  a 
  Unitrypa 
  his 
  

   description 
  becomes 
  intelligible, 
  which 
  it 
  would 
  not 
  be 
  if 
  he 
  

   were 
  describing 
  a 
  form 
  of 
  Fenestella 
  with 
  prominent 
  carinae. 
  

  

  If 
  his 
  fig. 
  1 
  is 
  closely 
  examined 
  the 
  larger 
  portion 
  of 
  the 
  figure 
  

   will 
  be 
  seen 
  to 
  be 
  a 
  very 
  good 
  illustration 
  of 
  the 
  summits 
  of 
  the 
  

   carinas 
  and 
  connecting 
  scalaa 
  of 
  a 
  Unitrypa, 
  while 
  in 
  the 
  upper 
  

   left-hand 
  portion 
  of 
  the 
  figure 
  this 
  portion 
  is 
  broken 
  away 
  and 
  

   the 
  branches 
  below 
  are 
  shown. 
  Fig. 
  la 
  is 
  somewhat 
  mystifying, 
  

   especially 
  the 
  solidified 
  margin 
  at 
  the 
  left 
  of 
  the 
  figure 
  and 
  also 
  

   the 
  title 
  "fenestrules 
  enlarged." 
  Fig. 
  lb 
  is 
  an 
  illustration 
  of 
  

   worn 
  branches 
  and 
  would 
  serve 
  equally 
  well 
  for 
  a 
  Unitrypa 
  or 
  

   a 
  Fenestella. 
  Fig. 
  lc 
  is 
  ideal 
  and 
  incorrect; 
  Id 
  is 
  also 
  ideal 
  

   and 
  is 
  not 
  correct, 
  yet 
  shows 
  that 
  the 
  cell 
  apertures 
  and 
  conse- 
  

   quently 
  the 
  branches 
  occurred 
  beneath 
  another 
  structure, 
  which 
  

   I 
  maintain 
  was 
  the 
  summits 
  of 
  the 
  carinas 
  and 
  their 
  connecting 
  

   scalae, 
  but 
  fig. 
  le, 
  " 
  terraced 
  appearance 
  of 
  cells 
  broken 
  off 
  near 
  

  

  * 
  la 
  this 
  statement 
  Mr. 
  Ulrich 
  is 
  mistaken, 
  as 
  twenty-six 
  species 
  with 
  " 
  prominent 
  carina 
  

   expanded 
  at 
  the 
  summit 
  " 
  were 
  not 
  described 
  by 
  Prof. 
  Hall 
  under 
  Fenestella 
  or 
  under 
  any 
  other 
  

   genus. 
  

  

  