106 
PALEONTOLOGY OF NEW YORK. 
Fig. 80. 
Figs. 80-85. 
Fig. 81. 
Fig. 82. 
Fig. 83. 
Fig. 84. 
Fig. 85. 
Retzia Adrieni, de Verneuil. Consecutive sections to show internal structure of the umbonal regions. 
Fig. 80. Outline of the shell, showing location of next three sections. 
Fig. 81. Section across opening of foramen, with umbonal tube open on the back. 
Fig. 8'2. Section further down, showing attachment of the remnants of the tube to the deltidial plates. 
Fig. 83. Section near the hinge, showing last traces of tube adherent to the thickened deltidial plates. 
Figs. 84, 85. Sections from another individual, one across the foramen, the other beneath it; showing the continuity 
of the tube. (C.) 
Fig. 86. 
Fig.'87. 
Fig. 88. 
Fig. 89. 
Fig. 90. 
Fig. 95. Fig. 96. Fig. 97. Fig. 98. 
Figs. 86-98. Retzia Adrieni, de Verneuil. 
Fig. 86. Section just below the foramen; showing the entire umbonal tube. 
Fig. 87. Showing the adherence of the tube to the still divided and discrete deltidial plates. 
Figs. 88, 89. Sections at the umbo of the brachial valve; showing the internal coalescence of the deltidial plates, 
and the open tube. 
Fig. 90. Showing the dental lamelhe, and the median septum in the brachial valve. 
Fig. 91. Section just above the apex of the brachial valve; showing the last traces of the deltidial plates, which are 
here free. 
Fig. 92. Section at the apex of the brachial valve. 
Fig. 93. Section cutting the posterior extension of the median and lateral lobes of the hinge-plate. 
Fig. 94. The same features further down; showing also the appearance of the teeth, and the remnants of the dental 
lamellm bordering the muscular area of the pedicle-valve. 
Fig. 95. Section through the center of the hinge-plate; showing also the development of the dental sockets. 
Fig. 96. Section showing the ante-median crestof the hinge-plate. 
Fig. 97. The anterior edge of the hinge-plate and its supporting septum. 
Fig. 98. Section in front of the hinge-plate; showing the crura and median septum. (C.) 
