﻿818 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM. 
  volxx. 
  

  

  LYONSIEuLA 
  CORDATA, 
  new 
  species. 
  

   (Plate 
  XCV, 
  figs. 
  7,8.) 
  

  

  Shell 
  rather 
  large 
  and 
  firm 
  for 
  the 
  genus, 
  somewhat 
  translucent 
  

   bluish 
  white, 
  swollen, 
  cordate, 
  with 
  a 
  posterior 
  obtuse 
  prominence. 
  

   Umbos 
  prominent, 
  turned 
  forward 
  spirally; 
  beaks 
  small, 
  strongly 
  

   incurved. 
  Lunnle 
  small, 
  cordate, 
  defined 
  only 
  by 
  one 
  of 
  the 
  ordinary 
  

   fine 
  radial 
  ridges; 
  the 
  part 
  that 
  lies 
  immediately 
  under 
  the 
  beak 
  is 
  

   deeply 
  sunken 
  with 
  the 
  edge 
  pinched 
  up 
  into 
  a 
  prominent 
  keel. 
  The 
  

   antero 
  dorsal 
  margin 
  is 
  strongly 
  convex 
  and 
  prominent 
  iu 
  the 
  lunu- 
  

   lar 
  region, 
  but 
  not 
  so 
  high 
  as 
  the 
  umbos; 
  the 
  anterior 
  margin 
  is 
  but 
  

   slightly 
  convex 
  and 
  nearly 
  ijerpendicular 
  to 
  the 
  axis 
  of 
  the 
  shell; 
  the 
  

   ventral 
  margin 
  is 
  strongly 
  convex 
  and 
  somewhat 
  produced 
  in 
  the 
  mid- 
  

   dle, 
  farther 
  back 
  it 
  is 
  but 
  slightly 
  convex 
  ; 
  the 
  posterior 
  end 
  is 
  obtusely 
  

   rounded, 
  decidedly 
  prominent 
  l)ut 
  not 
  angular; 
  the 
  postero-dorsal 
  mar- 
  

   gin 
  is 
  a 
  little 
  convex 
  and 
  slopes 
  gradually. 
  The 
  surface 
  is 
  covered 
  

   with 
  about 
  sixty 
  delicate, 
  radiating, 
  raised 
  lines 
  or 
  riblets 
  which 
  are 
  

   crossed 
  by 
  fine 
  lines 
  of 
  growth, 
  the 
  tliiu, 
  brownish 
  or 
  grayish 
  green 
  

   ejjidermis 
  often 
  rising 
  into 
  small 
  i)oints 
  at 
  their 
  intersection, 
  especially 
  

   anteriorly 
  and 
  posteriorly; 
  these 
  riblets 
  become 
  coarser 
  and 
  more 
  dis 
  

   taut 
  anteriorly, 
  and 
  are 
  lacking 
  on 
  the 
  lunule. 
  The 
  ligament 
  is 
  thin 
  

   and 
  strong 
  and 
  extends 
  backward 
  along 
  nearly 
  the 
  whole 
  of 
  the 
  dorsal 
  

   margin 
  and 
  curves 
  spirally 
  under 
  and 
  around 
  the 
  beak 
  in 
  the 
  region 
  of 
  

   the 
  resilium, 
  so 
  that 
  the 
  two 
  come 
  almost 
  in 
  contact. 
  The 
  hinge 
  mar- 
  

   gin, 
  in 
  front 
  of 
  the 
  beak 
  and 
  iunular 
  area, 
  is 
  strongly 
  convex 
  and 
  pro- 
  

   tuberant, 
  rising 
  nearly 
  to 
  the 
  height 
  of 
  the 
  umbo; 
  posteriorly 
  it 
  is 
  

   convex 
  and 
  thin 
  in 
  both 
  valves; 
  in 
  the 
  left 
  one 
  it 
  is 
  strengthened 
  by 
  a 
  

   slight 
  marginal 
  rib 
  within 
  the 
  ligameutal 
  furrow; 
  both 
  of 
  these 
  are 
  less 
  

   evident 
  in 
  the 
  right 
  valve. 
  There 
  are 
  no 
  teeth 
  in 
  either 
  valve. 
  The 
  

   ossicle 
  is 
  relatively 
  large, 
  oblong, 
  somewhat 
  saddle-shaped, 
  luirrowest 
  

   and 
  truncated 
  anteriorly, 
  broadest 
  and 
  forked 
  posteriorly, 
  the 
  divisions 
  

   acute. 
  The 
  resilium 
  beneath 
  the 
  ossicle 
  is 
  well 
  developed, 
  dark 
  brown, 
  

   and 
  extends 
  forward 
  and 
  upward 
  to 
  the 
  margin, 
  beneath 
  the 
  beak. 
  

  

  Length 
  of 
  the 
  largest 
  specimen, 
  11 
  mm. 
  ; 
  height, 
  12 
  mm. 
  Another 
  is 
  

   11 
  mm. 
  long; 
  11.5 
  mm. 
  high; 
  9 
  mm. 
  broajcl. 
  

  

  Two 
  living 
  specimens 
  and 
  one 
  valve, 
  at 
  three 
  stations 
  between 
  X. 
  lat. 
  

   390 
  If)', 
  W. 
  long. 
  08° 
  8', 
  and 
  N. 
  lat. 
  37o 
  38' 
  40", 
  W. 
  long. 
  73° 
  16' 
  30", 
  in 
  

   1,123 
  to 
  1,825 
  fathoms, 
  1881-188(5. 
  

  

  Family 
  LYONSID^. 
  

  

  LYONSIA 
  GRANULIFERA, 
  new 
  species. 
  

  

  (Plato 
  XCV, 
  fig. 
  1.) 
  

  

  Shell 
  oblong, 
  truncated 
  posteriorly, 
  narrowed 
  and 
  rounded 
  anteriorly. 
  

   Umbo 
  rather 
  prominent 
  with 
  the 
  beak 
  in 
  i'ront 
  of 
  the 
  middle 
  and 
  curved 
  

   forward; 
  Iunular 
  area 
  considerably 
  sunken. 
  Anterior 
  end 
  evenly 
  

  

  