﻿PKESTON 
  : 
  ON 
  LAND 
  SHELLS 
  FROM 
  ANGOLA. 
  53 
  

  

  Helicarion 
  Wklwitschi, 
  Morelet. 
  

  

  A 
  number 
  of 
  specimens, 
  in 
  all 
  stages 
  of 
  growth, 
  were 
  obtained 
  ; 
  

   they 
  are 
  quite 
  typical, 
  and 
  present 
  scarcely 
  any 
  variation. 
  

  

  Helicarion 
  sp. 
  (?). 
  

   Five 
  specimens, 
  probably 
  all 
  immature. 
  

  

  Thapsia 
  innocens, 
  11. 
  sp. 
  

  

  Shell 
  discoidal, 
  depressed, 
  thin, 
  hyaline, 
  polished, 
  light 
  j^ellowish- 
  

   brown 
  horn 
  colour; 
  whorls 
  8, 
  regularly 
  increasing 
  in 
  size; 
  sutures 
  

   impressed, 
  narrowly 
  margined 
  below; 
  perforation 
  moderately 
  wide; 
  

   labrum 
  simple, 
  acute 
  ; 
  aperture 
  broadly, 
  obliquely 
  sublunate. 
  Alt. 
  

   2'5, 
  diam. 
  maj. 
  5*25 
  mm. 
  ; 
  aperture, 
  alt. 
  1*5, 
  diam. 
  2 
  mm. 
  

  

  Hob. 
  — 
  Two 
  hundred 
  miles 
  due 
  east 
  of 
  Loanda, 
  Angola. 
  

  

  Eleven 
  specimens; 
  allied 
  to 
  Helix 
  cerea, 
  Gould,' 
  from 
  Cape 
  Palmas, 
  

   Liberia, 
  but 
  smaller, 
  darker 
  in 
  colour, 
  more 
  depressed, 
  and 
  rather 
  more 
  

   closely 
  coiled, 
  the 
  perforation 
  is 
  also 
  wider, 
  and 
  the 
  sutures 
  are 
  

   narrowly 
  margined, 
  which 
  is 
  not 
  the 
  case 
  with 
  II. 
  cerect. 
  

  

  Cerastus 
  delicatula, 
  n.sp. 
  

  

  Shell 
  small, 
  thin, 
  elongately 
  turbinate, 
  pule 
  brown 
  ; 
  apex 
  flattened 
  ; 
  

   whorls 
  7, 
  rather 
  convex, 
  sculptured 
  with 
  fine, 
  closely 
  set, 
  somewhat 
  

   oblique, 
  transverse 
  costulse, 
  which 
  become 
  obsolete 
  on 
  the 
  base, 
  last 
  

   whorl 
  bearing 
  a 
  blunt 
  thread-like 
  carina 
  below 
  the 
  periphery; 
  sutures 
  

   well 
  impressed 
  ; 
  umbilicus 
  narrow, 
  deep, 
  parti 
  j^ 
  concealed 
  by 
  the 
  

   reflection 
  of 
  the 
  columella 
  ; 
  columella 
  descending 
  vertically 
  ; 
  labrum 
  

   simple; 
  aperture 
  ovate. 
  Alt. 
  8, 
  diam. 
  maj. 
  4-75 
  mm.; 
  aperture, 
  

   alt. 
  3, 
  diam. 
  2 
  mm. 
  

  

  Hah. 
  — 
  Two 
  hundred 
  miles 
  due 
  east 
  of 
  Loanda, 
  Angola. 
  

  

  Seven 
  adult 
  specimens 
  and 
  a 
  number 
  of 
  youno; 
  in 
  various 
  stages 
  of 
  

   growth. 
  The 
  species 
  may 
  be 
  likened 
  to 
  a 
  miniature 
  C. 
  Ahtjssinicus, 
  

   Riippell, 
  from 
  Abyssinia, 
  Central 
  India, 
  etc. 
  

  

  IIachis 
  electrinus, 
  Morelet. 
  

   One 
  adult 
  and 
  one 
  very 
  immature 
  specimen. 
  

  

  1 
  Proc. 
  Bost. 
  Soc. 
  Nat. 
  Hist., 
  1850, 
  vol. 
  iii, 
  p. 
  19i. 
  

  

  