788 Report oF THE STATE GEOLOGIST. 
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 lamelle which 
traverse the umbonal cavity and rest on the bottom of the shell. 
OTOP oT[oO 
Fic. 339. Fia. 340. Fie. 341. Fie. 342. Fie. 343. 
Frias. 339-343 —Retzia Adrieni, de Verneuil. Consecutive sections to show internal structur 
of the umbonal regions. 
Fie. 339 — Section across opening of foramen, with umb-nal tube open on the back. 
Fic. 340 —Section further down, showing attachment of the remnants of the tube to the 
deltidial plates. 
Fia. 341.— Section near the hinge, showing last traces of tube adherent to the thickened 
deltidial plates. 
Fias. 342, 343.—Sections from another individual, one across the foramen, the other beneath 
t; showing the continuity of the tube. 
Fie. 344, Fie. 345, Fie, 346. 
Fia. 347. Fig. 348, 
Fies. 346-358.— Retzia Adrieni, de Verneuil. 
Fic, 344.— Section just below the foramen; showing the entire umbonal tube. 
Fic. 345.— Showing the adherence of tke tube to the still divided and discrete deltidial plates. 
Figs. 346, 317. Sections at the umbo of the brachial valve; showing the internal coalescence 
of the deltidial plates, and the open tube. 
Fic. 348.— Showing the dental lamellz, and the median septum in the brachial valve. 
These lamellz 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 
