﻿982 
  Forty-seventh 
  Report 
  on 
  the 
  State 
  Museum. 
  

  

  entirely 
  concealed 
  by 
  incurvature. 
  The 
  cardinal 
  slopes 
  are 
  

   broad 
  and 
  smooth. 
  On 
  the 
  interior 
  of 
  the 
  pedicle-valve 
  the 
  

   teeth 
  are 
  rather 
  small 
  and 
  are 
  supported 
  by 
  thin 
  lamellae 
  which 
  

   traverse 
  the 
  umbonal 
  cavity 
  and 
  rest 
  on 
  the 
  bottom 
  of 
  the 
  shell. 
  

  

  a 
  ra 
  HE 
  El 
  

  

  Fig. 
  339. 
  Fig. 
  340. 
  

  

  Fig. 
  341. 
  

  

  Fig. 
  342. 
  

  

  Fig. 
  343. 
  

  

  T 
  jgk. 
  339-343 
  —Retzia 
  Adrieni, 
  de 
  Verneuil. 
  Consecutive 
  sections 
  to 
  show 
  internal 
  structur 
  

   of 
  the 
  utnbonal 
  regions. 
  

  

  Fig 
  339 
  —Section 
  across 
  opening 
  of 
  foramen, 
  with 
  umb<->nal 
  tube 
  open 
  on 
  the 
  back. 
  

  

  Fig. 
  340 
  — 
  Section 
  further 
  down, 
  showing 
  attachment 
  of 
  the 
  remnants 
  of 
  the 
  tube 
  to 
  the 
  

   deltidial 
  plates. 
  

  

  Fig. 
  34 
  ;.— 
  Section 
  near 
  the 
  hinge, 
  showing 
  last 
  traces 
  of 
  tube 
  adherent 
  to 
  the 
  thickened 
  

   deltidial 
  plates. 
  

  

  Figs 
  342, 
  343.— 
  Sections 
  from 
  another 
  individual, 
  one 
  across 
  the 
  foramen, 
  the 
  other 
  beneath 
  

   it; 
  showing 
  the 
  continuity 
  of 
  the 
  tube. 
  

  

  W 
  

  

  Fig. 
  344 
  

  

  Fig. 
  345. 
  

  

  Fig 
  346. 
  

  

  Fig. 
  347. 
  

  

  Fig. 
  348. 
  

  

  Figs. 
  346-358.— 
  Retzia 
  Adrieni, 
  de 
  Verneuil. 
  

   Fig. 
  344. 
  — 
  Section 
  just 
  below 
  the 
  foramen; 
  showing 
  the 
  entire 
  umbonal 
  tube. 
  

   Fig. 
  345.— 
  Showing 
  the 
  adherence 
  of 
  the 
  tube 
  to 
  the 
  still 
  divided 
  and 
  discrete 
  deltidial 
  plates. 
  

   Figs. 
  346, 
  347. 
  — 
  Sections 
  at 
  the 
  umbo 
  of 
  the 
  brachial 
  valve; 
  showing 
  the 
  internal 
  coalescence 
  

   of 
  the 
  deltidial 
  plates, 
  and 
  the 
  open 
  tube. 
  

   Fig. 
  348. 
  — 
  Showing 
  the 
  deatal 
  lamellae, 
  and 
  the 
  median 
  septum 
  in 
  the 
  brachial 
  valve. 
  

  

  These 
  lamellae 
  are 
  produced 
  forward 
  for 
  a 
  short 
  distance, 
  limit- 
  

   ing, 
  posteriorly, 
  the 
  muscular 
  area. 
  The 
  apical 
  portion 
  of 
  the 
  

   umbonal 
  cavity 
  contains 
  a 
  longitudinal 
  tube 
  attached 
  by 
  one 
  

   side 
  to 
  the 
  inner 
  surface 
  of 
  the 
  deltidial 
  covering. 
  Just 
  within 
  

  

  40 
  

  

  