ON NEW BRACHIOPODA. 121 
margin of valves equal; attached by the whole of the larger 
valve. The interior of the ventral valve shews under 
the deltideum three little ridges, between which are 
situated muscular depressions; towards the front of the 
shell are short expanded ribs. The interior of the dorsal 
valve has a rounded visceral cavity, surmounted by the 
bridge, and partly hidden by the supra-membraneal disk, 
which in this species is formed by two eircular platforms, 
on the outer edge of which, and scattered over its surface, 
are arranged a number of elevated granulations. These 
are divided in the centre by a long septum, from the base 
of which proceeds the outer granulated ridge, and beyond 
this is a small granulated margin. 
Obs. The interior of the ventral valve of this species is 
not unlike 7! serratum, but it wants the elevated front of 
that shell; and it may also be distinguished by its more 
oval shape and less produced beak. When the supra- 
membraneal disk is wanting, the dorsal valve shews two 
small oblong elevations on each side of the septum, as seen 
in the variety fig. 10. 
This little species is named in remembrance of that emi- 
nent and lamented pal&ontologist, Professor E. FORBES. 
It is from the inferior oolite of Dundry. 
THECIDEUM TRIANGULARIS.—D Orb. 
Plate 3, fig. 11—12. 
Shell triangular, longer than broad ; deltideum small, 
area flat; hinge line straight; small valve slightly convex. 
Interior of ventral valve divided by a straight ridge oceu- 
pying the length of the shell. Interior of the dorsal valve 
has a granulated marginal ridge, from the centre of which 
1854, PART 11. Q 
x“ 
