﻿114 
  PROCKKDINGS 
  OF 
  THK 
  MAT-ACOLOGICAL 
  SOCIETY. 
  

  

  intervals, 
  apparently 
  smooth 
  but 
  under 
  a 
  good 
  lens 
  showing 
  transverse 
  

   scratclies. 
  Median 
  valves 
  with 
  two 
  similar 
  ribs 
  forming 
  the 
  lateral 
  

   area; 
  the 
  ribs 
  obsoletely 
  -scaled, 
  probably 
  due 
  to 
  growth, 
  and 
  

   sometimes 
  appearing 
  nodulose. 
  Pleura 
  longitudinally 
  ridged, 
  the 
  

   ridges 
  continuing 
  over 
  the 
  jiigum, 
  about 
  twenty 
  to 
  the 
  half-valve, 
  

   closer 
  together 
  as 
  they 
  reach 
  the 
  jugum, 
  the 
  interstices 
  closely 
  

   latticed. 
  Tail-valve 
  with 
  Tnucro 
  median, 
  depressed, 
  posterior 
  slope 
  

   convex. 
  Anterior 
  area 
  sculptured 
  as 
  tlie 
  pleura, 
  posterior 
  area 
  as 
  

   the 
  anterior 
  valve 
  with 
  nine 
  ribs, 
  scaly 
  nodulose. 
  Girdle 
  covered 
  

   with 
  minute 
  rounded 
  scales, 
  deeply 
  grooved. 
  The 
  internal 
  coloration 
  

   white; 
  teeth 
  and 
  slitting 
  normal, 
  but 
  sutural 
  lamince 
  low 
  and 
  

   continuous, 
  the 
  sinus 
  onlj' 
  showing 
  as 
  a 
  slight 
  curve. 
  

  

  Type 
  from 
  Port 
  Arthur, 
  southern 
  Tasmania, 
  collected 
  by 
  E. 
  Mawle. 
  

  

  Lengtli 
  17, 
  breadth 
  9"5 
  mm. 
  A 
  larger 
  specimen 
  measures 
  

   24x 
  12 
  mm. 
  

  

  llange 
  : 
  southern 
  Tasmania, 
  collected 
  by 
  W. 
  L. 
  ^lay, 
  Dr. 
  Torr, 
  

   and 
  E. 
  Mawle. 
  

  

  Separable 
  at 
  sight 
  from 
  C. 
  antiquiis 
  (Reeve) 
  by 
  the 
  presence 
  of 
  the 
  

   longitudinal 
  ribs 
  on 
  the 
  jugal 
  area; 
  a 
  honeycomb 
  structure 
  occurs 
  on 
  

   the 
  jugum 
  of 
  C. 
  antiquus 
  (Reeve), 
  as 
  here 
  figured 
  (PI. 
  IV, 
  Fig. 
  5«') 
  

   for 
  comparison. 
  Other 
  differences 
  exist 
  in 
  tiie 
  keeling, 
  size 
  and 
  

   shape 
  of 
  girdle-scale, 
  elevation 
  of 
  mucro 
  of 
  posterior 
  valve, 
  and 
  

   conclusively 
  in 
  the 
  formation 
  of 
  the 
  sutural 
  laminae. 
  These 
  are 
  

   continuous, 
  whereas 
  they 
  are 
  widely 
  separated 
  in 
  tlie 
  species 
  

   C. 
  antiquus 
  (Reeve), 
  and 
  even 
  more 
  so 
  in 
  the 
  South 
  Australian 
  species. 
  

  

  19. 
  SvPHAROCniTON 
  MAUGEANUS, 
  U.Sp. 
  PI. 
  V, 
  Fig. 
  5. 
  

  

  Shell 
  large, 
  elongate 
  oval, 
  elevated, 
  valves 
  round-backed, 
  beaked. 
  

   Colour 
  : 
  blackish 
  brown, 
  with 
  a 
  black 
  stripe 
  down 
  the 
  jugum, 
  

   succeeded 
  on 
  each 
  side 
  by 
  a 
  pale 
  buff 
  stripe, 
  blotches 
  of 
  the 
  latter 
  

   colour 
  also 
  occurring 
  on 
  some 
  of 
  the 
  sides 
  of 
  the 
  valves. 
  Anterior 
  

   valve 
  sculptured, 
  with 
  about 
  sixteen 
  ribs 
  at 
  the 
  apex, 
  divaricating 
  so 
  

   that 
  over 
  thirty 
  can 
  be 
  counted 
  at 
  the 
  edge 
  ; 
  the 
  ribs 
  are 
  cut 
  by 
  

   growth 
  -lines 
  into 
  irregular 
  nodules. 
  Median 
  valves 
  with 
  the 
  lateral 
  

   areas 
  similarly 
  sculptured, 
  four 
  primary 
  ribs 
  becoming 
  six 
  to 
  eight 
  at 
  

   the 
  edges 
  ; 
  pleural 
  areas 
  sculptured 
  with 
  fine 
  slanting 
  longitudinal 
  

   threads, 
  becoming 
  obsolete 
  on 
  the 
  jugum 
  ; 
  these 
  are 
  crossed 
  by 
  

   distinct 
  growth-lines, 
  which 
  do 
  not, 
  however, 
  cause 
  nodules. 
  Tail- 
  

   valve 
  with 
  the 
  mucro 
  elevated 
  at 
  about 
  the 
  anterior 
  third, 
  posterior 
  

   slope 
  straiglit; 
  sculpture 
  on 
  anterior 
  portion 
  like 
  that 
  on 
  ])leura 
  of 
  

   median 
  valves 
  ; 
  posterior 
  portion 
  sculptured 
  like 
  the 
  anterior 
  A'alve, 
  

   twelve 
  primary 
  ribs 
  being 
  noted, 
  and 
  as 
  many 
  secondary 
  ones. 
  

   Internal 
  features 
  normal. 
  Girdle 
  covered 
  with 
  large 
  round 
  oval 
  

   scales, 
  finely 
  striated. 
  

  

  Type 
  from 
  Port 
  Arthur, 
  southern 
  Tasmania. 
  

  

  Length 
  52, 
  breadth 
  31 
  mm. 
  A 
  large 
  specimen 
  measures 
  61 
  X 
  40 
  mm. 
  

  

  liange 
  : 
  southern 
  Tasmania. 
  

  

  The 
  history 
  of 
  the 
  genus 
  Sypharochiton 
  in 
  Australia 
  is 
  complex. 
  

   Chiton 
  pelhsserpentis 
  was 
  described 
  in 
  1834 
  by 
  Quoy 
  & 
  Gaimard 
  

   from 
  New 
  Zealand. 
  Gray 
  in 
  1843 
  added 
  another 
  species, 
  Chiton 
  

  

  