NOTES ON THE BRITISH JURASSIC BRACHIOPODA. 253 



Z. obesa, Moore, type from the Lower Lias of Stouts Hill, 

 Bitton. 



THECIDEA, Defrance, 1822, 

 Etym. — OyKT]^ a chest or case. 



This well-marked genus is considered by some authors to 

 be allied to the Terebratulidae by the presence of an internal 

 loop, although it differs in many respects from any of the 

 preceding genera, viz., by the absence of a foramen, its 

 thickened shell and granulated margin, as well as general 

 character and habits. 



Thecidea first makes its appearance in the Jurassic rocks, 

 where it is represented by fourteen species, including T. (?) 

 pygmseuvi and grauulosum, Moore. It is also found in the 

 Cretaceous rocks, and in existing seas is represented by the 

 sub-genus Lacazella, 



For our knowledge of the Liassic and Oolitic Thecidea^ we 



are mainly indebted to Charles Moore, in whose collection, 



in the Bath Museum, may be seen types of the following 



species : — 



T. bouchardii, Dav., from the Inferior Oolite of Dundry. 



T. duplicatum, Moore, ,, ,, ,, ,, 



T.forbesi, „ „ „ „ „ 



T. septatum ,, ,, „ ,, „ 



T. serratmn ., ,, ,, „ „ 



T. moorei, Dav., ,, Middle Lias of II minster. 



T. ornatnm ,, ,, Coral Rag, Lyneham, Wilts. 



T' (?)pygihmum „ „ „ „ „ 



Also described specimens of T. triangulares d' Orb., from 

 the Inferior Oolite of Dundry. 



The fossil Thecidea are uncommonly small in this country ; 

 on the Continent they are considerably larger. It is pro- 

 bably due to their being so small that they, and also Zellania 

 and Megathyris, are often overlooked by ^collectors. At the 

 request of Mr. Walker, a large quantity of the marly stuff 



