﻿INVERTEBRATES. 
  357 
  

  

  Heteroschisma 
  alternatum 
  and 
  H. 
  elongatum, 
  but 
  the 
  summit 
  of 
  the 
  

   pyramids 
  extends 
  considerably 
  above 
  the 
  crests 
  of 
  the 
  oral 
  plates, 
  

   while 
  in 
  the 
  two 
  others 
  the 
  summit 
  scarcely 
  reaches 
  the 
  level 
  of 
  

   the 
  peristome 
  ; 
  it 
  also 
  has 
  narrower, 
  almost 
  linear 
  ambulacra, 
  

   against 
  slightly 
  petaloid 
  ones 
  in 
  the 
  others, 
  and 
  these 
  are 
  divided 
  

   by 
  the 
  food 
  groove 
  only, 
  while 
  the 
  Louisville 
  species 
  have 
  three 
  in- 
  

   dented 
  lines 
  along 
  their 
  surface. 
  It 
  further 
  differs 
  from 
  H. 
  alter- 
  

   natum 
  in 
  having 
  straight, 
  and 
  not 
  convex 
  sides 
  along 
  the 
  calyx, 
  

   and 
  a 
  conical, 
  more 
  sharply 
  pointed 
  basal 
  cup. 
  

  

  It 
  is 
  barely 
  possible 
  that 
  Pentremites 
  subtruncatus, 
  Hall 
  (Geol. 
  Rep. 
  

   Iowa, 
  Vol. 
  I, 
  Pt. 
  II, 
  p. 
  435), 
  is 
  identical 
  with 
  this 
  species. 
  A 
  com- 
  

   parison 
  is 
  impossible 
  as 
  Hall's 
  description 
  is 
  so 
  indistinct, 
  that 
  not 
  

   even 
  the 
  genus 
  can 
  be 
  identified. 
  He 
  refers 
  it 
  to 
  forms 
  like 
  Pen- 
  

   tremites 
  Rheinwardti, 
  and 
  mentions 
  "ovarian 
  openings," 
  which 
  if 
  

   present 
  suggest 
  a 
  very 
  different 
  thing. 
  Should, 
  however, 
  hereafter, 
  

   the 
  identity 
  be 
  proved, 
  the 
  name 
  must 
  be 
  placed 
  as 
  a 
  synonym 
  under 
  

   Heteroschisma 
  gracile. 
  

  

  Position 
  and 
  locality, 
  etc. 
  : 
  Found 
  near 
  the 
  top 
  of 
  the 
  Hamilton 
  

   group, 
  Alpena, 
  Mich. 
  

  

  (The 
  type 
  specimens 
  are 
  in 
  the 
  collections 
  of 
  Prof. 
  Barris, 
  and 
  

   Charles 
  Wachsmuth.) 
  

  

  Description 
  of 
  some 
  new 
  Blastoidsfrom 
  the 
  Hamilton 
  Group, 
  by 
  W. 
  H. 
  Barms. 
  

  

  El^iacrinus, 
  Roemer.* 
  

  

  Syn.— 
  Pentremites 
  Troost, 
  1841, 
  Gth 
  Eep. 
  Geol. 
  Tennessee, 
  

  

  Nueleocrinus 
  Conrad, 
  1843, 
  Jour. 
  Aead. 
  Nat. 
  Sci. 
  Phila. 
  Vol. 
  VIII, 
  p. 
  280. 
  

  

  Olivanites 
  Troost, 
  1850, 
  Cat. 
  name. 
  

  

  Elreacrinus 
  Roemer, 
  1851, 
  Monog. 
  Blastoidea, 
  p. 
  55. 
  

  

  Olivanites 
  Lyon, 
  1857. 
  Geol. 
  Sur. 
  Kent, 
  Vol. 
  Ill, 
  p. 
  490. 
  

  

  Nueleocrinus 
  Lyon 
  and 
  Cass, 
  1859; 
  Hall, 
  1862; 
  Shumard, 
  1862. 
  

  

  Elreacrinus 
  Shumard, 
  1866, 
  Trans. 
  St. 
  L. 
  Acad. 
  Sci., 
  p. 
  368. 
  

  

  Nueleocrinus, 
  Canadensis? 
  Montgomery, 
  1881; 
  Can. 
  Nat. 
  Vol. 
  X, 
  No. 
  2. 
  

  

  *At 
  the 
  suggestion 
  of 
  Mr. 
  Charles 
  Wachsmuth, 
  and 
  in 
  conformity 
  with 
  the 
  views 
  of 
  the 
  

   late 
  Dr. 
  Shumard 
  (Cat. 
  Palaeoz. 
  Poss., 
  in 
  the 
  Trans. 
  St. 
  L. 
  Acad. 
  Sci., 
  1866, 
  p. 
  368), 
  I 
  

   give 
  Roemer's 
  later 
  name 
  Elceacrinus 
  preference 
  over 
  Nueleocrinus, 
  Conrad. 
  Conrad 
  s 
  

   entire 
  description 
  is 
  as 
  follows: 
  "Nueleocrinus 
  Conrad. 
  The 
  genus 
  differs 
  from 
  Pentre- 
  

   mites, 
  Say, 
  in 
  having 
  only 
  one 
  perforation, 
  which 
  is 
  central. 
  "In 
  this 
  description, 
  the 
  only 
  

   distinguishing 
  character 
  is 
  erroneous, 
  the 
  accompanying 
  figure 
  poor 
  and 
  incorrect, 
  and 
  

   Hall's 
  excellent 
  descriptions 
  of 
  Nueleocrinus 
  were 
  published 
  ten 
  years 
  later 
  than 
  those 
  of 
  

   Elaeacrinus. 
  Roemer. 
  in 
  proposing 
  the 
  latter 
  name, 
  gave 
  a 
  good 
  definition 
  of 
  the 
  genus. 
  

   He 
  found 
  the 
  central 
  aperture 
  which 
  Conrad 
  had 
  pronounced 
  ' 
  the 
  only 
  perforation 
  a! 
  

   the 
  top," 
  closed 
  in 
  perfect 
  specimens, 
  and 
  surrounding 
  it 
  he 
  discovered 
  one 
  large 
  and 
  ten 
  

   smaller 
  openings. 
  

  

  