﻿JURASSIC AND TRIASSIC BRACHIOPODA. 



109 



Volume of this work, I will reproduce Mr. Moore's account of its interior : — " Interior of 

 ventral valve shows two produced teeth, between which, under the deltidium, is a small 

 central ridge, on either side of which are muscular depressions, beyond which -are the 

 impressions of the larger muscles. About the middle of the cavity of the valve commence 

 striated ribs, which become more produced as they approach the inner front of the shell, 

 terminating at the margin of the valve in small bosses or knobs. The interior of the 

 dorsal valve has a deep frontal margin, comprising nearly half the area of the valve, 

 chiefly occupied by a series of deep grooves, which received, when closed the bosses of the 

 ventral valve ; where the grooves cease, a flattened striated band occurs. Within the 

 margin is an elevated ridge, with granulations, united at the top by a straight ridge, 

 forming a bridge over an elongated visceral cavity, and at the bottom by a broad septum. 

 The inner portion of the valve is occupied by a calcified supra-membraneal disk, divided 

 into two lobes by the central septum. This beautiful species of Thecideum is the only one 

 which presents so peculiar a frontal margin. It is very rarely found perfect, only two 

 specimens showing the supra-membraneal disk having been obtained." 



This shell occurs in the Inferior Oolite of Dun dry. It is a minute species being less 

 than a line in length and width. 



58. Thecidium septatum, Moore. Dav., 



and 



Thecideum septatum, Moore. 



Inferior Oolite, Dundry. It is scarcely 

 width. 



Supplementary Appendix to vol. i, p. 30, 

 Sup., PI. XII, figs. 22 to 24. 



Proceed, of the Somersetshire Archaeological and 

 Nat. Hist. Soc, vol. for 1854, p. 119, pi. ii, 

 figs. 13 to 16. 



half a line in length, but a little more in 



59. Thecidium Porbesii, Moore. Sup., PI. XII, figs. 6 to 9. 



Thecideum Forbesii, Moore. Proc. of the Somersetshire Archaeological and Nat. 



Hist. Soc, vol. for 1854, p. 120, pi. iii, figs. 8—10. 



Shell minute, transversely oval, wider than long. Hinge-line straight, about half the 

 width of the shell. Dorsal valve much depressed or of small convexity. Surface 

 smooth. Ventral valve attached by the whole of its lower surface ; beak straight, area 

 triangular, flat ; deltidium occupying about one third of the surface of the area. In the 

 interior of the ventral valve, under the deltidium, are two converging ridges with a straight 



