ON NEW BKACHIOPODA. 167 



downvvards towards the front of tlie shell, wliere tliey 

 bifurcate, and are tlicn again unIted to the shell at its 

 inner sides. Above the septum and attached laraellte a 

 band occurs, forming a bridge over the visceral cavity. 

 This is iinited to the granulated ridge, which thus com- 

 pletely surrounds the inner portion of the valve. 



Obs. — The preservation of the loop as shown in the 

 enlarged fig, 3, pl. IL, 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 careful manipu- 

 lation in dissecting er opening up the valves. Many of 

 the interiors of the Thecididas are very beautiful ; but I 

 have never yet seen any species equalling in delicacy of 

 structure that under consideration. It is from the Coral 

 Eag of Lyneham, Wilts, where it is not uncommon. 



Thecideum pygm^um, Moore. 

 PI. IL, figs. 4-7. 



Shell microscopic, longitudinally oval ; both valves con- 

 vex; attached to other bodies at the upper part of the 

 ventral valve ; beak slightly produced ; area short ; delti- 

 dium ill defined. A thin raised ridge passes round the 

 front and sides of the dorsal valve, until it reaches the 

 dental sockets. It is without a central septum, nearly 

 alvvays present in other species, the only ornamentation 

 within the ridge being numerous punetuations. 



Obs. — This shell is very numerous in the Coral Rag of 

 Lyneham, associated with the T. ornatum and the T. 

 triangularis. I have been unable to trace any passage into 

 either of the above species, otherwise it might have been 

 considercd a young stage of one of them. As it is alto- 

 gether different in character, and as the shell, though so 



