﻿Polyzoa 
  of 
  the 
  St. 
  Lawrence. 
  425 
  

  

  seas 
  and 
  is 
  well 
  represented 
  in 
  the 
  St. 
  Lawrence. 
  The 
  

   Eschara 
  scabra 
  of 
  Fabricius, 
  subsequently 
  described 
  at 
  length 
  

   and 
  figured 
  by 
  Smitt, 
  is 
  a 
  member 
  of 
  it 
  and 
  the 
  first 
  of 
  which 
  

   we 
  have 
  any 
  notice. 
  Smitt 
  referred 
  this 
  species 
  and 
  kindred 
  

   forms 
  to 
  the 
  genus 
  Cellepora, 
  and 
  I 
  have 
  followed 
  him 
  (but 
  

   only 
  provisionally) 
  in 
  a 
  paper 
  (1877) 
  containing 
  descriptions 
  

   of 
  new 
  Arctic 
  Polyzoa. 
  Probably 
  Lorenz 
  is 
  right 
  in 
  regarding 
  

   them 
  as 
  a 
  distinct 
  generic 
  group, 
  though 
  his 
  diagnosis 
  may 
  

   require 
  amendment. 
  They 
  are 
  properly 
  detached 
  from 
  Celle- 
  

   pora, 
  a 
  group 
  which 
  has 
  already 
  been 
  dismembered 
  to 
  some 
  

   extent 
  by 
  Smitt, 
  and 
  which 
  awaits 
  a 
  more 
  thorough 
  revision. 
  

   The 
  species 
  included 
  in 
  the 
  genus 
  RJuvmphostomella 
  have 
  some 
  

   affinity 
  with 
  Mucronella, 
  but 
  they 
  are 
  differentiated 
  from 
  it 
  by 
  

   special 
  characters 
  and 
  a 
  general 
  habit 
  which 
  are 
  sufficiently 
  

   significant. 
  

  

  Lorenz's 
  diagnosis 
  of 
  his 
  new 
  genus 
  is 
  as 
  follows 
  : 
  — 
  

  

  Zocecia 
  generally 
  oval, 
  very 
  regularly 
  alternate, 
  slightly 
  

   prominent 
  ; 
  orifice 
  terminal, 
  broad, 
  semicircular, 
  closed 
  by 
  a 
  

   thin 
  membranous 
  operculum, 
  surrounded 
  in 
  front 
  and 
  at 
  the 
  

   sides 
  by 
  an 
  elevated 
  peristome, 
  with 
  a 
  central 
  notch, 
  on 
  one 
  

   side 
  of 
  which 
  an 
  avicularium 
  is 
  usually 
  placed 
  ; 
  the 
  half 
  of 
  

   the 
  peristome 
  bearing 
  the 
  avicularium, 
  as 
  compared 
  with 
  the 
  

   other, 
  very 
  strongly 
  developed, 
  and 
  often 
  standing 
  out 
  like 
  

   the 
  rostrum 
  of 
  a 
  Gellepora. 
  Ooecium 
  hemispherical 
  and 
  per- 
  

   forated. 
  Zoarium 
  unilamellar. 
  

  

  ]N'ow 
  one 
  of 
  the 
  principal 
  characters 
  included 
  in 
  this 
  descrip- 
  

   tion 
  — 
  the 
  elevated 
  peristome, 
  cleft 
  in 
  front 
  — 
  is 
  by 
  no 
  means 
  

   constant 
  throughout 
  the 
  group. 
  In 
  R. 
  plicata, 
  Smitt, 
  R. 
  bi- 
  

   laminata, 
  Hincks, 
  and 
  R. 
  radiatula, 
  id., 
  it 
  is 
  present, 
  and 
  

   a 
  very 
  striking 
  feature 
  ; 
  but 
  there 
  is 
  no 
  trace 
  of 
  it 
  in 
  R. 
  ovata, 
  

   Smitt, 
  R. 
  costata, 
  Lorenz, 
  and 
  R. 
  scabra, 
  Fabricius 
  (?). 
  It 
  

   cannot 
  therefore 
  be 
  employed 
  with 
  propriety 
  as 
  a 
  principal 
  

   diagnostic. 
  

  

  Verrill 
  refers 
  R. 
  scabra 
  and 
  R. 
  ovata 
  to 
  u 
  Mucronella 
  (re- 
  

   stricted) 
  " 
  * 
  ; 
  but 
  as 
  his 
  restriction 
  excludes 
  from 
  the 
  genus 
  

   all 
  forms 
  which 
  are 
  not 
  furnished 
  with 
  " 
  lateral 
  avieularia 
  on 
  

   one 
  or 
  both 
  sides 
  of 
  the 
  zocecial 
  aperture 
  " 
  and 
  destitute 
  of 
  

   " 
  the 
  median 
  avicularium," 
  these 
  species 
  have 
  certainly 
  no 
  

   claim 
  to 
  a 
  place 
  in 
  it. 
  

  

  On 
  the 
  whole 
  I 
  should 
  be 
  inclined 
  to 
  adopt 
  Lorenz's 
  genus 
  

   with 
  a 
  revised 
  diagnosis 
  : 
  — 
  

  

  Zocecia 
  oval, 
  the 
  walls 
  thin, 
  of 
  delicate 
  shining 
  material, 
  

   smooth 
  (frequently 
  traversed 
  by 
  radiating 
  costai), 
  entire 
  

   (destitute 
  of 
  pores) 
  ; 
  orifice 
  ample, 
  arched 
  above, 
  lower 
  mar- 
  

  

  * 
  " 
  Notice 
  of 
  Eecent 
  Additions 
  to 
  the 
  Marine 
  Invertebrata 
  of 
  the 
  

   North-eastern 
  Coast 
  of 
  America," 
  &c, 
  Proc. 
  U.S. 
  Nat. 
  Mus. 
  i;?7U, 
  p. 
  10.3. 
  

  

  