﻿NO. 
  1139. 
  DEEP-WATER 
  MOLLUSCA—VERBILL 
  AND 
  BUSH. 
  791 
  

  

  CRYPTODON 
  (AXINULUS) 
  INEQUALIS, 
  new 
  species. 
  

   (Plate 
  XC, 
  figs. 
  1, 
  2.) 
  

  

  Shell 
  small, 
  somewhat 
  oblong, 
  with 
  the 
  anterior 
  end 
  much 
  the 
  longer. 
  

   Umbos 
  rather 
  prominent, 
  beaks 
  elevated, 
  curved 
  strongly 
  forward, 
  so 
  

   as 
  to 
  leave 
  a 
  small, 
  deep 
  lunular 
  area. 
  The 
  antero-dorsal 
  margin 
  is 
  at 
  

   first 
  nearly 
  straight, 
  sloping 
  but 
  little, 
  and 
  is 
  nearly 
  parallel 
  with 
  the 
  

   ventral 
  margin; 
  the 
  anterior 
  end 
  is 
  produced, 
  broadly 
  and 
  evenly 
  

   rounded; 
  the 
  ventral 
  margin 
  is 
  much 
  less 
  rounded, 
  with 
  the 
  middle 
  

   portion 
  almost 
  straight 
  for 
  a 
  short 
  distance, 
  toward 
  the 
  posterior 
  end 
  

   it 
  is 
  subtruucate 
  and 
  slightly 
  angulated; 
  the 
  postero-dorsal 
  margin 
  is 
  

   convex 
  and 
  slopes 
  rapidly; 
  a 
  very 
  slight 
  depression 
  runs 
  from 
  the 
  

   beak 
  to 
  the 
  postero- 
  ventral 
  margin, 
  but 
  is 
  so 
  slight 
  as 
  to 
  be 
  scarcely 
  

   worthy 
  the 
  name 
  of 
  plication 
  or 
  fold; 
  posterior 
  to 
  this 
  there 
  is 
  a 
  dis- 
  

   tinct 
  submarginal 
  ridge 
  separated 
  by 
  a 
  rather 
  deej) 
  groove, 
  from 
  the 
  

   ligamental 
  area, 
  which 
  is 
  long 
  and 
  narrow. 
  The 
  surface 
  aj^peai's 
  to 
  

   the 
  naked 
  eye 
  nearly 
  smooth, 
  bluish 
  white; 
  under 
  the 
  microscope 
  it 
  is 
  

   marked 
  by 
  slight, 
  raised, 
  concentric 
  ridges 
  and 
  faint 
  undulations, 
  

   which 
  are 
  the 
  most 
  regular 
  and 
  distinct 
  on 
  the 
  umbos. 
  In 
  addition 
  to 
  

   these 
  the 
  whole 
  surface, 
  when 
  highly 
  magnified, 
  has 
  a 
  fine 
  fibrous 
  

   appearance; 
  on 
  some 
  parts 
  there 
  are 
  remnants 
  of 
  a 
  thin, 
  pale 
  yellow- 
  

   ish 
  epidermis. 
  The 
  hinge-margin 
  is 
  distinctly 
  thickened, 
  with 
  a 
  slight 
  

   l^rotuberance 
  directly 
  under 
  the 
  beak, 
  where 
  it 
  is 
  thicker 
  than 
  else- 
  

   where. 
  The 
  posterior 
  ligament 
  is 
  rather 
  large 
  and 
  strong, 
  and 
  occu- 
  

   pies 
  a 
  conspicuous 
  groove 
  extending 
  from 
  under 
  the 
  beak 
  about 
  one- 
  

   third 
  the 
  length 
  of 
  the 
  postero 
  dorsal 
  margin. 
  

  

  Length, 
  4..") 
  mm.; 
  height, 
  4.25 
  mm.; 
  thickness, 
  about 
  4 
  mm. 
  

  

  A 
  few 
  specimens 
  have 
  been 
  found 
  in 
  14 
  to 
  49 
  fathoms, 
  at 
  about 
  eleven 
  

   stations 
  north 
  of 
  Cape 
  Cod, 
  in 
  Casco 
  Bay, 
  and 
  in 
  Halifax 
  Harbor, 
  

   1873-1879. 
  

  

  CRYPTODON 
  (AXINULUS) 
  SIMPLEX, 
  new 
  species. 
  

  

  (Plate 
  XCII, 
  figs. 
  3,4.) 
  

  

  Shell 
  small, 
  thin, 
  fragile, 
  translucent 
  bluish 
  white, 
  somewhat 
  inflated, 
  

   nearly 
  circular 
  in 
  outline 
  and 
  without 
  any 
  posterior 
  undulations. 
  Beaks 
  

   small, 
  acute, 
  slightly 
  prominent, 
  turned 
  forward. 
  Antero-dorsal 
  mar- 
  

   gin 
  excavated 
  in 
  front 
  of 
  the 
  beaks 
  and 
  convex 
  farther 
  forward; 
  ante- 
  

   rior 
  margin 
  broadly 
  and 
  evenly 
  rounded 
  and, 
  with 
  the 
  ventral 
  margin, 
  

   forms 
  nearly 
  a 
  circular 
  curve; 
  the 
  posterior 
  margin 
  similarly 
  rounded, 
  

   but 
  slightly 
  flattened 
  in 
  the 
  middle; 
  postero-dorsal 
  margin 
  broadly 
  

   convex 
  without 
  any 
  distinct 
  angulation 
  posteriorly. 
  The 
  surface 
  is 
  

   nearly 
  smooth 
  and 
  somewhat 
  glossy 
  on 
  the 
  umbos; 
  it 
  is 
  marked 
  by 
  

   rather 
  indistinct, 
  small, 
  concentric 
  waves 
  or 
  undulations 
  and 
  micro- 
  

   scopic 
  lines 
  of 
  growth. 
  Interior 
  somewhat 
  shining. 
  The 
  hinge-margin 
  

   is 
  thin, 
  delicate, 
  and 
  very 
  simple, 
  with 
  but 
  a 
  very 
  slight 
  thickening 
  in 
  

   the 
  region 
  of 
  the 
  beak; 
  a 
  narrow 
  groove 
  for 
  the 
  ligament 
  is 
  visible 
  just 
  

  

  