﻿378 
  Transactions. 
  — 
  Zoology. 
  

  

  Art. 
  LI. 
  — 
  Descriptions 
  of 
  three 
  new 
  Species 
  of 
  Opistliobranchiate 
  MoUusca, 
  

   from 
  Now 
  Zealand. 
  By 
  T. 
  F. 
  Cheeseman, 
  F.L.S., 
  Curator 
  of 
  the 
  Auck- 
  

   land 
  Museum. 
  

  

  Plate 
  XYI. 
  

  

  {Read 
  before 
  the 
  Auckland 
  Institute, 
  22nd 
  October, 
  1877.] 
  

  

  From 
  a 
  number 
  of 
  new 
  species 
  of 
  Opistliobranchiate 
  Mollusca, 
  collected 
  

  

  in 
  or 
  near 
  Auckland 
  Harbour, 
  I 
  liave 
  selected 
  for 
  description 
  the 
  three 
  

  

  following 
  prominent 
  forms 
  : 
  — 
  

  

  1. 
  Pleurobeanchus 
  ornatus, 
  n. 
  sp. 
  (PI. 
  XVI., 
  figs. 
  1,2.) 
  

  

  Body 
  3-4 
  inches 
  long, 
  broadly 
  elliptical, 
  depressed, 
  nearly 
  equally 
  

   rounded 
  at 
  both 
  ends, 
  colour 
  varying 
  from 
  pale 
  buff 
  to 
  a 
  clear 
  reddish 
  

   brown, 
  with 
  irregularly 
  disposed 
  blotches 
  of 
  a 
  rich 
  dark 
  red-brown 
  ; 
  mantle 
  

   large, 
  extending 
  over 
  and 
  concealing 
  both 
  head 
  and 
  foot, 
  quite 
  smooth, 
  

   margin 
  thin, 
  entire 
  ; 
  dorsal 
  tentacles 
  short, 
  stout, 
  abruptly 
  truncate, 
  finely 
  

   transversely 
  wrinkled, 
  approximate 
  at 
  their 
  origin, 
  but 
  gradually 
  diverging 
  

   at 
  their 
  apices 
  ; 
  colour 
  reddish 
  brown 
  tipped 
  with 
  white 
  ; 
  eye-specks 
  black, 
  

   placed 
  a 
  little 
  distance 
  behind 
  the 
  tentacles, 
  embedded 
  in 
  the 
  integument, 
  

   but 
  appearing 
  through 
  it 
  ; 
  oral 
  tentacles 
  united 
  in 
  front 
  by 
  a 
  thin 
  semi- 
  

   circular 
  expansion 
  which 
  forms 
  a 
  veil 
  concealing 
  the 
  mouth, 
  and 
  which 
  is 
  

   carried 
  in 
  advance 
  of 
  the 
  foot 
  ; 
  mouth 
  roundish, 
  with 
  fleshy 
  lips 
  ; 
  buccal 
  

   plates 
  two, 
  regularly 
  reticulated 
  ; 
  odontoxohore 
  with 
  numerous 
  rows 
  of 
  

   similar 
  unciform 
  teeth. 
  Branchial 
  plume 
  placed 
  in 
  the 
  groove 
  between 
  the 
  

   foot 
  and 
  the 
  mantle, 
  very 
  large, 
  composed 
  of 
  about 
  22-24 
  pectinations; 
  foot 
  

   oblong, 
  thin 
  and 
  flexible, 
  pale 
  waxy 
  white. 
  

  

  Shell 
  internal, 
  i^ 
  to 
  f 
  inch 
  long, 
  squarish 
  oblong, 
  thin 
  and 
  membranous, 
  

   semitransparent, 
  slightly 
  iridescent, 
  closely 
  marked 
  with 
  somewhat 
  irregular 
  

   concentric 
  strise 
  or 
  folds 
  ; 
  colour 
  varying 
  from 
  nearly 
  white 
  to 
  pale 
  pinkish 
  

   or 
  tawny 
  brown. 
  Spire 
  minute, 
  obscure, 
  mouth 
  occupymg 
  the 
  whole 
  of 
  the 
  

   under 
  surf 
  ace. 
  

  

  My 
  first 
  specimens 
  of 
  this 
  handsome 
  species 
  were 
  obtained 
  from 
  under 
  

   stones 
  between 
  tide-marks 
  in 
  Auckland 
  Harbour 
  ; 
  where, 
  however, 
  it 
  is 
  by 
  

   no 
  means 
  common. 
  Near 
  Waiwera 
  and 
  in 
  some 
  other 
  localities 
  on 
  the 
  

   Hauraki 
  Gulf 
  it 
  is 
  much 
  more 
  frequently 
  met 
  with. 
  It 
  is 
  easily 
  kept 
  alive 
  

   in 
  an 
  aquarium, 
  but 
  is 
  very 
  sluggish 
  in 
  its 
  movements. 
  

  

  2. 
  Pleurobranch^a 
  nov^-z;eai,andi;e, 
  n, 
  sp. 
  (Plate 
  XVL, 
  fig. 
  3.) 
  

  

  Body 
  oval, 
  convex, 
  thick 
  and 
  fleshy, 
  smooth 
  and 
  lubricous 
  to 
  the 
  touch, 
  

   but 
  the 
  whole 
  surface 
  nevertheless 
  covered 
  with 
  minute 
  packers 
  and 
  folds. 
  

   Colour 
  light 
  grey, 
  copiously 
  streaked 
  with 
  irregular 
  anastomosing 
  lines 
  of 
  

   dark 
  greyish-brown, 
  and 
  sprinkled 
  with 
  numerous 
  minute 
  and 
  almost 
  

  

  