﻿162 
  PROCEEDINGS 
  OF 
  TttK 
  MALACOLOGICAL 
  SOCIETV. 
  

  

  by 
  an 
  inverted 
  V-sluiped 
  line 
  directed 
  obliquely 
  outwards 
  to 
  tbe 
  

   shell-wall. 
  It 
  is 
  unfortunate 
  that 
  through 
  bad 
  preservation 
  there 
  is 
  

   no 
  evidence 
  of 
  the 
  large 
  invaginated 
  siphuncle. 
  The 
  testiferous 
  

   structure 
  which 
  once 
  covered 
  the 
  cast 
  must 
  have 
  been 
  extremely 
  

   thin, 
  as 
  the 
  finely 
  semicircular 
  surface 
  striations 
  are 
  veiy 
  distinct, 
  

   being 
  closely 
  arranged, 
  regular, 
  and 
  parallel 
  with 
  the 
  rounded 
  

   margin 
  of 
  the 
  aperture 
  ; 
  certain 
  growth 
  periods 
  appear 
  to 
  be 
  also 
  

   represented 
  by 
  a 
  few 
  more 
  or 
  less 
  obscure, 
  distant, 
  and 
  strongly 
  

   curved 
  ridges. 
  There 
  is 
  besides 
  what 
  is 
  supposed 
  to 
  be 
  an 
  impression 
  

   of 
  the 
  annular 
  band, 
  which 
  would 
  indicate 
  the 
  position 
  of 
  the 
  shell 
  - 
  

   muscle 
  by 
  which 
  the 
  animal 
  was 
  attached. 
  It 
  is 
  represented 
  by 
  two 
  

   pai'allel, 
  nearly 
  contiguous, 
  curved 
  lines, 
  which 
  bend 
  over 
  to 
  the 
  

   umbilical 
  centre 
  in 
  front, 
  and 
  in 
  the 
  other 
  direction 
  pursues 
  an 
  

   obli(juoly 
  downward 
  coui'se 
  to 
  the 
  periphery, 
  differing 
  from 
  the 
  ti'ue 
  

   NautUus, 
  which 
  shows 
  a 
  similar 
  marking 
  but 
  of 
  greater 
  elevation 
  and 
  

   more 
  ovally 
  arched. 
  Some 
  distance 
  below, 
  another 
  line 
  can 
  be 
  

   traced 
  which 
  is 
  more 
  or 
  less 
  parallel 
  with 
  the 
  upper 
  curvatuie 
  

   marking, 
  while 
  the 
  space 
  between 
  would 
  represent 
  the 
  area 
  of 
  

   attachment 
  of 
  the 
  shell-muscle. 
  Still 
  further 
  down, 
  there 
  ap])eai- 
  

   to 
  be 
  traces 
  of 
  the 
  septal 
  band, 
  which 
  takes 
  a 
  sinuous 
  course 
  across 
  

   the 
  bod3--ch 
  amber. 
  

  

  According 
  to 
  the 
  terminology 
  adopted 
  by 
  Mr. 
  L. 
  E. 
  Griffin 
  ' 
  in 
  

   connexion 
  w-ith 
  muscle-markings 
  on 
  the 
  inner 
  surface 
  of 
  the 
  body- 
  

   chamber 
  of 
  the 
  recent 
  Naiitilm, 
  it 
  is 
  stated 
  that 
  there 
  are 
  three 
  

   " 
  aponeurotic 
  bauds 
  " 
  extending 
  from 
  the 
  deeply 
  arched 
  attachment 
  

   area 
  of 
  the 
  shell-muscle,' 
  viz. 
  one 
  dorsal 
  connecting 
  with 
  the 
  surface 
  

   of 
  the 
  central 
  chambered 
  region, 
  and 
  two 
  ventral, 
  the 
  upper 
  of 
  which 
  

   is 
  known 
  as 
  the 
  " 
  anterior 
  ventral 
  aponeurotic 
  band", 
  while 
  a 
  distant 
  

   lower 
  one 
  is 
  named 
  the 
  " 
  posterior 
  ventral 
  aponeurotic 
  band 
  ", 
  both 
  

   being 
  directed 
  across 
  from 
  the 
  umbilical 
  wall 
  to 
  the 
  inner 
  surface 
  of 
  

   the 
  peripheral 
  region. 
  It 
  would 
  seem, 
  therefore, 
  that 
  the 
  terms 
  

   "annular" 
  and 
  " 
  septal" 
  bands 
  formerly 
  in 
  use 
  for 
  s])ecit'ying 
  these 
  

   muscle-markings 
  should 
  now 
  be 
  superseded 
  by 
  regarding 
  them 
  as 
  

   "aponeurotic" 
  bands, 
  which 
  refers 
  to 
  the 
  membrane 
  surrounding 
  

   the 
  muscular 
  organs. 
  

  

  Our 
  lately 
  deceased 
  member, 
  Mr. 
  G. 
  C. 
  Crick,- 
  carried 
  out 
  some 
  

   valuable 
  researches 
  on 
  the 
  muscle 
  - 
  markings 
  observed 
  in 
  the 
  

   Ammonold 
  group 
  of 
  the 
  Cephalopoda, 
  which 
  have 
  been 
  of 
  wide 
  

   interest. 
  The 
  reference 
  on 
  the 
  present 
  occasion 
  to 
  corresponding 
  

   markings 
  in 
  the 
  genus 
  Atnrta 
  appears 
  to 
  be 
  made 
  for 
  the 
  first 
  time. 
  

  

  The 
  less 
  complete 
  lateral 
  aspect 
  of 
  this 
  fossil 
  discloses 
  a 
  large 
  

   cavity 
  near 
  the 
  peripheral 
  margin 
  of 
  the 
  upper 
  part 
  of 
  the 
  body- 
  

   chamber 
  and 
  well 
  below 
  its 
  surface, 
  containing 
  what 
  appears 
  to 
  

   resemble 
  a 
  depressed 
  sub-oval 
  Ostreiform 
  valve 
  with 
  evidence 
  of 
  

  

  ^ 
  "The 
  Anatomy 
  of 
  Nautilus 
  'pom2)ilias 
  " 
  : 
  Mem. 
  Nat. 
  Acad. 
  Sci. 
  (\Vasliiugi,on)i 
  

  

  vol. 
  viii, 
  1900, 
  p. 
  151, 
  pi. 
  i. 
  

   " 
  "On 
  the 
  Muscular 
  Attachment 
  of 
  the 
  Animal 
  to 
  its 
  Shell 
  in 
  some 
  Fossil 
  

  

  Cephalopoda 
  (Ammonoidea) 
  " 
  : 
  Trans. 
  Linn. 
  See. 
  London, 
  ser. 
  II, 
  

  

  Zoology, 
  vol. 
  vii, 
  1898, 
  pp. 
  71-113, 
  pis. 
  xvii-xx. 
  

  

  