96 
THE GEOLOGIST. 
ON NEW BRACHIOPODA, AND ON THE DEVELOPMENT 
OF THE LOOP IN TEREBRATELLA. 
By Charles Moore, F.G S. 
(Continued from jpage 445, vol. iii.) 
Thecideum. Defrance. 
Thecidewm omatum. Moore. PL, ii., figs. 1 — 3. 
Shell ineqnivalve ; punctuate, rather rugose, front deep, rounded ; 
attached by a considerable portion of the ventral valve ; beak shghtly 
incurved ; deltidium small and depressed. The ventral valve is flat- 
tened on its under side. Its interior is surrounded by an elevated, 
slightly granulated margin. Under the deltidium are seen two 
raised oval processes, separated by a longitudinal septum, which 
occupies the greater length of the shell. The exterior of the dorsal 
valve is rugose and flattened. The interior possesses a narrow, thin, 
punctuated mai^gin, immediately succeeding which is a ridge of single 
granulations, which are stronger towards the frontal margin, gradu- 
ally disappearing as the ridge passes upwards. Springing from the 
centre of this gTanulated ridge is a septum, slightly tapering from its 
base, on either side strongly serrated, between which is a central 
longitudinal gToove. The septum occupies nearly the whole height 
allowed by the cavity of the shell, and divides it to nearly three- 
fourths of its length. From the top of the septum there are thro^Ti 
ofi" two extremely delicate lamellse, forming a loop which curves 
downwards towards the front of the shell, where they bifuo-cate, and 
are then again united to the shell at its inner sides. Above the sep- 
tum and attached lamellae a band occurs, forming a bridge over the 
visceral cavity. This is united to the gTanulated ridge, which thus 
completely surrounds the inner portion of the valve. 
Ohs. — The preservation of the loop as shown in the enlarged 
fig. 3, plate ii., is remarkable, since in the original specimen it is in 
substance scarcely thicker than the finest unspun silk, and extremely 
brittle. The interiors of the Brachiopoda are only to be developed 
by carefal manipulation in dissecting or opening up the valves. 
Many of the interiors of the Thecididse are very beautifal ; but I 
have never as yet seen any species equalhng in dehcacy of structure 
that under consideration. It is from the Coral Rag of Lyneham; 
Wilts, where it is not uncommon. 
Thecideum pygmceum. Moore. PI. ii., figs. 4 — 7. 
Shell microscopic, longitudinally oval ; both valves convex ; 
attached to other bodies at the upper part of the ventral valve ; beak 
slightly produced ; area short j deltidium ill defined. A thin raised 
