﻿990 
  Forty- 
  seventh 
  Report 
  on 
  tee 
  State 
  Museum. 
  

  

  long, 
  slender 
  and 
  nearly 
  vertical 
  crura. 
  The 
  hinge-plate 
  is 
  not 
  

   connected 
  with 
  the 
  lateral 
  portions 
  of 
  the 
  shell, 
  but 
  is 
  supported 
  

   by 
  two 
  slightly 
  divergent, 
  upright 
  lamellae 
  which 
  extend 
  to 
  the 
  

   bottom 
  of 
  the 
  valve 
  ; 
  as 
  the 
  valve 
  in 
  this 
  region 
  is 
  deep, 
  these 
  

   lamellae 
  are 
  very 
  conspicuous. 
  The 
  crura 
  widen 
  as 
  they 
  approach 
  

   the 
  apices 
  of 
  the 
  primary 
  lamellae, 
  and 
  form 
  their 
  union 
  with 
  

   these 
  by 
  a 
  short, 
  abrupt 
  lateral 
  curve. 
  The 
  spiral 
  cones 
  are 
  

   approximate, 
  their 
  apices 
  lateral, 
  the 
  ribbon 
  making 
  eight 
  or 
  

   nine 
  volutions 
  in 
  the 
  adult 
  individual. 
  The 
  umbonal 
  blades 
  are 
  

   broad 
  for 
  one-third 
  their 
  length, 
  narrowing 
  abruptly 
  in 
  front 
  

   of 
  the 
  jugum. 
  The 
  jugum 
  is 
  situated 
  posteriorly, 
  and 
  is 
  con- 
  

   structed 
  as 
  follows: 
  Two 
  slender 
  lateral 
  processes 
  are 
  given 
  off 
  

   from 
  the 
  primary 
  lamellae, 
  which 
  are 
  directed 
  forward 
  in 
  low, 
  do 
  wn- 
  

  

  Figs. 
  364, 
  365. 
  Two 
  views 
  of 
  the 
  jugum 
  of 
  Eumetria 
  Verneuiliana, 
  Hall. 
  

  

  ward 
  curves, 
  and 
  near 
  their 
  extremities 
  turn 
  inward 
  and 
  upward, 
  

   meeting 
  at 
  a 
  point 
  just 
  behind 
  the 
  center 
  of 
  the 
  shell-cavity. 
  

   From 
  their 
  point 
  of 
  union 
  a 
  single 
  process 
  is 
  extended 
  backward 
  

   at 
  an 
  abrupt 
  angle 
  and 
  with 
  a 
  very 
  gentle 
  downward 
  curve, 
  

   terminating 
  just 
  in 
  front 
  of 
  the 
  apices 
  of 
  the 
  primary 
  lamellae 
  

   and 
  above 
  the 
  bases 
  of 
  the 
  spiral 
  cones 
  ; 
  its 
  extremity 
  is 
  broad- 
  

   ened 
  and 
  bifurcated, 
  these 
  secondary 
  processes, 
  however, 
  extend- 
  

   ing 
  but 
  a 
  very 
  short 
  distance. 
  The 
  posterior 
  edges 
  of 
  the 
  lateral 
  

   branches 
  of 
  the 
  jugum 
  and 
  of 
  the 
  primary 
  lamellae 
  may 
  be 
  finely 
  

   fimbriated. 
  

  

  There 
  is 
  usually 
  no 
  trace 
  of 
  a 
  median 
  septum 
  in 
  this 
  valve, 
  but 
  

   occasionally 
  an 
  obscure 
  ridge 
  is 
  preserved. 
  No 
  muscular 
  mark- 
  

   ings 
  have 
  been 
  observed. 
  

  

  48 
  

  

  