﻿U. 
  S. 
  B. 
  F,— 
  Doc. 
  804. 
  

  

  Plate 
  V. 
  

  

  FIG. 
  1.— 
  A 
  THREE-RIDGE 
  (QUADRULA 
  PLICATA) 
  WHICH 
  WAS 
  INJURED 
  AND 
  CONTAINED 
  

  

  NO 
  PEARLS. 
  

  

  FIG. 
  2.— 
  ONE 
  VALVE 
  OF 
  A 
  THREE-RIDGE 
  (Q. 
  PLICATA), 
  SHOWING 
  THE 
  

   CAVITY 
  FROM 
  WHICH 
  AN 
  EMBEDDED 
  58-GRAIN 
  TURTLEBACK 
  PEARL 
  

   WAS 
  TAKEN, 
  WHICH 
  WHEN 
  PEELED- 
  PRODUCED 
  A 
  FINE 
  20-GRAIN 
  

   HIGH-BUTTON. 
  

  

  This 
  shell, 
  on 
  account 
  of 
  the 
  distortion 
  caused 
  by 
  the 
  pearly 
  growth, 
  is 
  somewhat 
  kidney-shaped. 
  

  

  