﻿THE 
  OPERCULUM 
  OF 
  THE 
  GENUS 
  BURSA 
  (RANELLA). 
  

  

  By 
  the 
  llev. 
  A. 
  H. 
  Cooke, 
  Sc.D., 
  F.Z.S. 
  

  

  Read 
  IMh 
  January, 
  1916. 
  

  

  W. 
  H. 
  Dall, 
  in 
  his 
  well-lviiown 
  and 
  admirable 
  paper, 
  ^ 
  " 
  An 
  Historical 
  

   and 
  Systematic 
  Review 
  of 
  tlie 
  Froj;;-Shells 
  and 
  Tritons," 
  draws 
  up 
  

   a 
  classification, 
  which 
  results 
  in 
  the 
  following 
  grouping: 
  — 
  

  

  Genus 
  BunsA. 
  

  

  A. 
  Sub-genus 
  Bursa. 
  

   Operculum 
  with 
  lateral 
  nucleus 
  : 
  

  

  («) 
  Sect. 
  Bursa 
  {spinosa, 
  Lam.). 
  

  

  {b) 
  Sect. 
  Marsupma 
  {spadicea, 
  Mtf., 
  or 
  crassa, 
  Dillw.). 
  

  

  (c) 
  Sect. 
  Chasmuiheca 
  {foliata, 
  Brod.). 
  

  

  Operculum 
  with 
  apical 
  nucleus 
  : 
  

  

  (d) 
  Sect. 
  Banella 
  {bufonia, 
  Gmel.). 
  

  

  {e) 
  Sect. 
  Lampadopsis 
  {rhodostoma, 
  Beck). 
  

   (/) 
  Sect. 
  Colubrellina 
  {conditus, 
  Gmel.). 
  

  

  B. 
  Sub-genus 
  Aspa. 
  

  

  Sect. 
  Aspa 
  {marginata, 
  Gmel.). 
  

  

  C. 
  Sub-genus 
  Bufonaria. 
  

  

  (a) 
  Sect. 
  Crossata 
  [ventricosa, 
  Brod.). 
  

  

  (b) 
  Sect. 
  Bufonaria 
  {scrobilator 
  \_sic], 
  L.). 
  

  

  (c) 
  Sect. 
  Craspedotrito7i 
  {^convolutus, 
  Brod.). 
  

  

  It 
  will 
  be 
  noticed 
  that 
  the 
  characteristics 
  of 
  the 
  operculum, 
  given 
  

   in 
  the 
  above 
  classification, 
  affect 
  only 
  one 
  of 
  the 
  three 
  sub-genera 
  

   {Bursa), 
  while 
  of 
  the 
  operculum 
  of 
  the 
  two 
  remaining 
  sub-genera 
  

   [Aspa, 
  Bufonaria) 
  nothing 
  is 
  stated. 
  

  

  Dall 
  further 
  remarks: 
  " 
  According 
  to 
  Adams 
  the 
  Banella 
  have 
  the 
  

   operculum 
  ovate, 
  with 
  an 
  apical 
  or 
  subapical 
  nucleus, 
  Avhile 
  Gray 
  

   speaks 
  of 
  it 
  as 
  half-ovate 
  with 
  a 
  central, 
  lateral, 
  or 
  internal 
  nucleus 
  ; 
  

   })robably 
  it 
  varies 
  in 
  the 
  different 
  groups 
  as 
  in 
  the 
  Tritons 
  ; 
  in 
  Banella 
  

   foliata 
  it 
  is 
  figured 
  as 
  concentric, 
  witli 
  the 
  nucleus 
  mid-lateral. 
  One 
  

   cannot 
  safely 
  generalize 
  on 
  the 
  character 
  until 
  the 
  operculum 
  of 
  more 
  

   species 
  is 
  known." 
  

  

  In 
  view 
  of 
  this 
  last 
  remark 
  I 
  venture 
  to 
  put 
  on 
  record 
  the 
  facts, 
  so 
  

   far 
  as 
  they 
  are 
  known 
  to 
  me, 
  of 
  a 
  considerable 
  number 
  of 
  species 
  

   of 
  the 
  genus 
  Bursa. 
  If 
  students 
  to 
  whom 
  are 
  known 
  the 
  opercula 
  of 
  

   other 
  species 
  not 
  in 
  the 
  list 
  Avill 
  gradually 
  add 
  to 
  the 
  number, 
  a 
  more 
  

   or 
  less 
  complete 
  body 
  of 
  evidence 
  will 
  in 
  the 
  end 
  be 
  accumulated. 
  

   No 
  final 
  classification 
  of 
  a 
  group 
  can 
  be 
  regarded 
  as 
  settled 
  until 
  full 
  

   information 
  of 
  this 
  kind 
  is 
  in 
  our 
  possession. 
  

  

  It 
  must 
  be 
  premised 
  that 
  Dall 
  published 
  no 
  list 
  of 
  species 
  contained 
  

   in 
  each 
  of 
  his 
  several 
  groups 
  or 
  sections, 
  but 
  only 
  a 
  type 
  species 
  in 
  

   each 
  case. 
  I 
  have 
  therefore 
  worked 
  the 
  list 
  as 
  interpreted 
  by 
  the 
  

  

  ^- 
  Smiths. 
  Coll., 
  xlvii, 
  1904, 
  pp. 
  114-44. 
  

  

  