‘BRACHIOPODA. 901 
and supported by a median septum. In the brachial valve the 
cardinal process is prominent, concave on its inner surface and 
lies in the plane of the valve. The median septum is broad, 
acute at its anterior extremity. Between each of its lateral walls 
and the marginal border of the valve are elongate depressions 
filled with a loose tissue of calcareous spicules. 
Fies. 653-655. Davidsonella sinuata, Deslongchamps (sp.). (DESLONGCHAMPS.) 
Type, Davidsonella sinuata, Deslongchamps (sp.). 
Distribution. Lias. 
Lyttonia, Waagen. 1883. 
Shells of great size, highly inequivalve and very irregular; fre- 
quently with broad lateral 
expansions. 
Pedicle valve convex, thick: 
apex not distinct ; hinge-line 
short and straight; teeth 
faintly developed. On the 
interior are numerous ridges 
extending in slight curves 
toward the lateral margins; 
in the median line a smooth 
space bearing a central vertical 
ridge. Brachial valve opercu- } 2 
3 % Lyttonia nobilis, Waagen. 
liform, not extending to the Fie. 656. Cardinal part of apedicle-valve; show- 
margins of the opposite valve. ng the hinge-line, median and lateral septa. 
Cardinal process small and eo 
bilobed ; median surface of the interior with divergent grooves 
corresponding with the ridges of the other valve. 
y 153 
Fig, 656. 
