866 Report oF THE State GEOLOGIST. 
Hemiptychina, Waagen. 1882. 
Plicated biconvex shells without dental plates, but with the 
hinge-structure and brachidium of Dimrasma. 
Fia. 505. Hemiptychina Himalayensis, Davidson. 
A portion of the in‘erior; showing the absence of dental plates in the pedicle-valve, and the 
DievasMa-like brachidium. CWAAGEN ) 
Type, Hemiptychina Himalayensis, Davidson (sp.). 
Distribution. Carboniferous — Permian. 
Beecheria, Hall. 1893. 
(Plate 53, figs. 1-3.) 
Non-plicated shells in which the dental plates are absent or 
represented only by faint ridges which do not reach the bottom 
of the pedicle-valve. 
The peculiar myiferous hinge-plate of Dmtasma is wholly 
merged with the valve, but the crural ridges are stlll retained and 
the descending lamellz originate from them at the bottom of the 
Dat 
Fie. 506. Beecheria sublevis, Waagen (sp.) 
Dorsal view: showing the smooth exterior. (WAAGEN.) 
Fic. 507. Beecheria Davidsoni, Hall. 
An enlarged profile of the brachidium; showing the manner in which lamellz arise from the 
bottom of the valve, the broad posterior jugal processes and the much narrower descend- 
ing lamellz. (he anterior transverse or reflected band is not fully retained. 
valve in very much the same way asin Dierasma. The crural 
apophyses are broad and erect, there being no part of the descend- 
ing branches behind them. Sometimes the brachial valve retains 
a low muscular impression which has the form of the platform of 
Diecasma. 
Type, Beecheria Davidsoni, Hall. 
Distribution. Carboniferous. 
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