﻿ANATOMY 
  AND 
  AFFINIT'IKS 
  OF 
  Till) 
  TliOOHlD^. 
  53 
  

  

  Evidence 
  of 
  torsion 
  Laving 
  affected 
  the 
  alimentary 
  canal 
  is 
  

   famished 
  by 
  the 
  displaced 
  condition 
  of 
  the 
  posterior 
  portion 
  of 
  

   the 
  radula-sac 
  (vide 
  p. 
  50) 
  and 
  by 
  the 
  rotation 
  of 
  the 
  right 
  

   oesophageal 
  pouch 
  to 
  the 
  left 
  side, 
  and 
  vice 
  versa 
  (38, 
  

   p. 
  392). 
  Torsion 
  of 
  the 
  crop 
  and 
  its 
  associated 
  structures 
  has 
  

   been 
  described 
  by 
  Woodward 
  (46, 
  p. 
  236) 
  in 
  Pleuro- 
  

   tomaria, 
  and 
  in 
  Turbo 
  and 
  other 
  genera 
  by 
  Amadrut 
  (1) 
  

  

  Just 
  beyond 
  the 
  point 
  at 
  which 
  the 
  radula-sac 
  crosses 
  over 
  

   the 
  dorsal 
  surface 
  of 
  the 
  crop 
  this 
  latter 
  becomes 
  much 
  

   smaller 
  and 
  thicker 
  walled, 
  and 
  may 
  be 
  regarded 
  as 
  the 
  oeso- 
  

   phagus 
  (figs. 
  40, 
  45, 
  te.) 
  ; 
  it 
  passes 
  backwards 
  and 
  ulti- 
  

   mately 
  opens 
  into 
  the 
  posterior 
  portion 
  of 
  the 
  stomach. 
  

  

  The 
  stomach 
  (figs. 
  39, 
  40, 
  45, 
  .s-;^.) 
  is 
  situated 
  underneath 
  

   and 
  behind 
  the 
  right 
  kidney, 
  and 
  is 
  a 
  large 
  sac 
  divided 
  into 
  

   an 
  oesophageal 
  or 
  posterior 
  and 
  an 
  intestinal 
  or 
  anterior 
  

   chamber. 
  From 
  the 
  posterior 
  region 
  of 
  the 
  stomach 
  there 
  

   arises 
  a 
  large 
  spiral 
  cjecum 
  {sp. 
  c), 
  a 
  structure 
  character- 
  

   istic 
  of 
  the 
  majority 
  of 
  the 
  Diotocardia. 
  

  

  There 
  is 
  a 
  slight 
  difference 
  in 
  the 
  shape 
  of 
  the 
  stomachs 
  in 
  

   the 
  members 
  of 
  the 
  sub-genus 
  Gibbula 
  and 
  those 
  of 
  the 
  

   sub-genus 
  Calliostoma. 
  In 
  the 
  latter 
  this 
  organ 
  is 
  more 
  or 
  

   less 
  U-shaped, 
  and 
  the 
  spiral 
  cfscum 
  arises 
  at 
  the 
  bend 
  of 
  the 
  

   U, 
  near 
  the 
  confluence 
  of 
  the 
  oesophageal 
  and 
  intestinal 
  cham- 
  

   bers; 
  the 
  intestine 
  leads 
  directly 
  out 
  of 
  the 
  latter, 
  and 
  

   docs 
  not 
  coil 
  on 
  itself 
  in 
  the 
  manner 
  in 
  which 
  it 
  loops 
  in 
  

   T. 
  lineatus 
  (fig. 
  45) 
  and 
  other 
  species 
  of 
  the 
  sub-genus 
  

   G 
  i 
  b 
  b 
  u 
  1 
  a. 
  

  

  In 
  Calliostoma 
  the 
  spiral 
  cascum 
  consists 
  of 
  many 
  turns, 
  

   and 
  the 
  apex 
  of 
  the 
  spire 
  can 
  be 
  distinctly 
  recognised 
  on 
  the 
  

   outer 
  surface 
  of 
  the 
  visceral 
  mass. 
  In 
  Gribbula, 
  on 
  the 
  

   contrary, 
  the 
  spiral 
  Ciscum 
  consists 
  of 
  few 
  turns, 
  and 
  the 
  

   apex 
  of 
  the 
  spire 
  is 
  deeply 
  buried 
  in 
  the 
  substance 
  of 
  the 
  

   liver, 
  only 
  the 
  basal 
  coil 
  being 
  visible 
  on 
  the 
  exterior. 
  

  

  When 
  the 
  interior 
  of 
  the 
  stomach 
  is 
  examined 
  (fig. 
  45) 
  two 
  

   conspicuous 
  folds, 
  arising 
  in 
  the 
  vicinity 
  of 
  the 
  oesophageal 
  

   aperture, 
  are 
  plainly 
  visible. 
  These 
  folds 
  are 
  continued 
  up 
  to 
  

   and 
  throughout 
  the 
  whole 
  length 
  of 
  the 
  spiral 
  ctecum, 
  en- 
  

  

  