898 Report OF THE STATE GEOLOGIST. 
which is somewhat incurved over the broad, arched cardinal area. 
Deltidium conspicuously developed. Interior of both valves with 
broad, thickened granulose marginal areas. In the pedicle-valve 
the teeth are small and parallel; the adductor muscles rest upon 
a short median plate lying directly in front of the deltidium, at 
each side of which is the transversely oval scar of the diductors. 
Visceral area iarge, smooth and divided medially by a granulated 
Fias. 648, 644. Thecidea radiata, o, deltidium; kk, teeth; ab, adductors, e, diductors; h, car- 
dinal process; i, cardinal plate; g, brachial supports. (Suzss.) 
ridge. In the brachial valve the cardinal process is large, erect 
and subtriangular. The median septum branches repeatedly 
from its posterior extremity forward, and this forms a series of 
depressions or grooves of unequal length in which lay the lobes 
of the brachia. 
Type, Thecidea papillata, Schlotheim (sp.). 
Distribution. Cretaceous. 
Subgenus Lacazella, Munier—Chalmas. 1880. 
Shells subtrigonal, solidly attached by the apex of the pedicle- 
valve; surface smooth or with concentric growth lines. Pedicle- 
valve with conspicuous cardinal area and deltidium; muscular 
plate concave, small, free at its anterior extremity. In the 
brachial valve the cardinal process is strong, subrectangular, 
concave toward the base, and projected beyond the hinge. The 
cavities of the brachial lobes in two or three unequal pairs. 
Animal with short alimentary canal; embryos developed in a 
pouch or marsupium situated at the bottom of the pedicle-valve, 
and attached to the brachia by a pair of long cilia. 
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