﻿796 
  PBOCEEDrxaS 
  of 
  the 
  national 
  museum. 
  vol.xx. 
  

  

  AXINODON 
  ELLIPTICUS, 
  new 
  species. 
  

   (Plates 
  XC, 
  figs. 
  5, 
  6; 
  XCII, 
  lig. 
  1.) 
  

  

  Shell 
  small, 
  nearly 
  smooth, 
  swollen, 
  transversely 
  elliptical 
  and 
  some- 
  

   what 
  oblong, 
  with 
  rather 
  prominent 
  umbos 
  and 
  with 
  the 
  beaks 
  con- 
  

   siderably 
  behind 
  the 
  middle 
  and 
  curved 
  forward. 
  The 
  antero-dorsal 
  

   margin 
  is 
  decidedly 
  convex 
  and 
  somewhat 
  excurved, 
  the 
  anterior 
  end 
  

   is 
  longer 
  and 
  a 
  little 
  broader 
  than 
  the 
  ])osterior 
  ; 
  both 
  are 
  nearly 
  evenly 
  

   rounded; 
  the 
  ventral 
  margin 
  is 
  broadly 
  rounded 
  and 
  nearly 
  straight 
  

   for 
  a 
  short 
  distance 
  along 
  the 
  middle; 
  the 
  postero-dorsal 
  margin 
  is 
  con- 
  

   vex 
  and 
  merges 
  into 
  the 
  posterior 
  end 
  in 
  a 
  regular 
  curve. 
  The 
  lunular 
  

   area 
  is 
  rather 
  distinct, 
  but 
  without 
  any 
  very 
  definite 
  boundary. 
  The 
  

   surface 
  is 
  nearly 
  smooth, 
  covered 
  only 
  with 
  fine, 
  close 
  lines 
  of 
  growth, 
  

   which, 
  under 
  the 
  microscope, 
  appear 
  as 
  delicate, 
  raised 
  lines, 
  separated 
  

   by 
  grooves 
  of 
  about 
  the 
  same 
  width; 
  this 
  sculjjture 
  is 
  very 
  regular 
  

   over 
  most 
  of 
  the 
  surface, 
  but 
  on 
  the 
  umbos 
  some 
  of 
  the 
  ridges 
  are 
  so 
  

   large 
  as 
  to 
  appear 
  like 
  small 
  undulations. 
  The 
  interior 
  surface 
  is 
  

   smooth 
  and 
  white; 
  the 
  muscular 
  scars 
  are 
  indistinct; 
  the 
  hinge-margin 
  is 
  

   rather 
  thin; 
  the 
  posterior 
  ligament 
  is 
  prominent, 
  wedge-shaped, 
  widest 
  

   distally, 
  and 
  occupies 
  a 
  distinct 
  groove 
  covering 
  the 
  whole 
  breadth 
  

   and 
  extending 
  about 
  one 
  third 
  the 
  length 
  of 
  the 
  postero-dorsal 
  margin 
  

   and 
  running 
  forward 
  under 
  the 
  beaks. 
  In 
  the 
  left 
  valve 
  there 
  are 
  two 
  

   slightly 
  raised, 
  minute, 
  obscure, 
  rounded 
  teeth 
  under 
  the 
  beak, 
  of 
  which 
  

   the 
  anterior 
  is 
  a 
  little 
  more 
  distinct 
  than 
  the 
  other; 
  farther 
  forward, 
  

   and 
  separated 
  from 
  the 
  latter 
  by 
  a 
  slight 
  notch, 
  there 
  is 
  an 
  elongated 
  

   thickening 
  of 
  the 
  margin 
  forming 
  a 
  sort 
  of 
  lateral 
  tooth 
  or 
  lamina 
  and 
  

   separated 
  from 
  the 
  outer 
  edge 
  by 
  a 
  narrow 
  groove. 
  In 
  the 
  right 
  valve 
  

   the 
  anterior 
  tooth-like 
  thickening 
  is 
  less 
  distinct 
  and 
  there 
  is 
  only 
  a 
  

   very 
  slight 
  rounded 
  swelling 
  of 
  the 
  lunular 
  margin 
  under 
  the 
  beak. 
  

  

  Length, 
  3.5 
  mm.; 
  height, 
  3 
  mm. 
  

  

  Two 
  live 
  specimens 
  (So. 
  35175), 
  station 
  2096, 
  E. 
  lat. 
  39° 
  22' 
  20", 
  W. 
  

   long. 
  70O 
  52' 
  20", 
  in 
  1,451 
  fathoms, 
  1S83. 
  

  

  LE^^TAXINUS, 
  new 
  genus. 
  

  

  Type. 
  — 
  Lepiaxinvs 
  mimitus, 
  new 
  species. 
  

  

  Shell 
  small, 
  short-ovate, 
  iiiequilateral, 
  with 
  the 
  anterior 
  end 
  the 
  

   longer, 
  and 
  rounded, 
  and 
  the 
  posterior 
  end 
  tapered 
  and 
  angulated, 
  

   with 
  a 
  slight 
  plication. 
  Hinge-i)late 
  well 
  developed, 
  with 
  a 
  delicate, 
  

   lateral 
  tooth 
  on 
  both 
  sides 
  of 
  the 
  beak 
  in 
  the 
  right 
  valve, 
  and 
  one 
  pos- 
  

   terior 
  lateral 
  tooth 
  in 
  the 
  left 
  valve; 
  in 
  both 
  valves 
  with 
  the 
  proximal 
  

   end 
  of 
  the 
  hinge-plate 
  enlarged 
  and 
  thickened 
  near 
  the 
  beak, 
  that 
  of 
  

   the 
  left 
  valve 
  most 
  developed 
  and 
  rising 
  into 
  a 
  blunt 
  tooth-like 
  promi- 
  

   nence. 
  Ligament 
  commencing 
  under 
  the 
  beak 
  and 
  running 
  back 
  on 
  

   the 
  ventral 
  side 
  of 
  the 
  posterior 
  hinge-plate, 
  so 
  that 
  for 
  the 
  greater 
  

   part 
  of 
  its 
  length 
  it 
  is 
  internal. 
  

  

  