BracwiopopA. 789 
the outer opening of the foramen this tube appears to have been 
closed on all sides, but further toward the cardinal margin it 
becomes split along the back or outer surface, diminishing in size 
downward and disappearing entirely before the cardinal margin 
is reached. In sections made across the vertical foramen it is 
seen that the tube extends within the deltidial covering, and 
forms a subcircular enfolding of testaceous matter from the 
margins of the foramen. 
ma 
AN 
Fia. 349. Fia, 350. Fia. 351. Fia, 352. 
Fia. 349.— Section just above the apex of the brachial valve; showing the last traces of the 
deltidial plates, which are here free. 
fie. 350.—Section at the apex of the brachial valve. 
fia. 351.—Section cutting the posterior extension of the median and lateral lobes of the 
hinge-plate. 
Fie. 352.— The same features further down; showing also the appearance of the teeth, and 
the remnants of the dental Jamellze bordering the muscular area of the pedicle-valve. 
Fie. 353. . 354. Fic, 355. Fig. 356. 
Fic. 353.—Section through the center of the hinge-plate; showing also the development of 
the dental sockets. : 
Fie. 354.— Section showing the ante-median crest of the hinge-plate. 
Fic. 355.— The anterior edge of the hinge-plate and its supporting septum, 
Fia. 356.— Section in front of the hinge-plate; showing the crura and median septum. 
In the brachial valve the hinge-plate is subquadrate on its 
upper surface, its posterior margin somewhat crescentic, the 
horns of the crescent extending into the umbonal cavity of the 
opposite valve; this character, however, is not so highly devel- 
oped as in Eumerria. The structure of this plate appears to be 
essentially similar ito that of Husrepia; at all events, the tent- 
shaped crural supports of Eumerrta are absent ; there is, however, 
no trace here of the ligulate, curved process which occurs in 
Al 
