﻿JURASSIC AND TRIASSIC BRACHIOPODA. 



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the dorsal valve. In some specimens both branches appear to be united almost in their 

 entire length, while they are more or less widely separated in others. 



48. Thecidium ? pygmjsum, Moore. Sup., PI. XIII, figs. 16, 16 a, b, c. 



Thecideum ptgmjEUM, Moore. The Geologist, vol. iv, p. 96, pi. ii, figs. 4 — 7, 1861. 



" Shell microscopic, longitudinally oval ; both valves convex ; attached to other bodies 

 at the upper part of the ventral valve ; beak slightly produced ; area short ; deltidium 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 always present in 

 other species, the only ornamentation within the ridge being numerous punctations." 



" Obs. — This shell is very numerous in the Coral Rag of Lyneham, associated with 

 T. ornatum and T. triangulate. I have been unable to trace any passage into either of 

 the above species, otherwise it might have been considered a young stage of one of them. 

 As it is altogether different in character, and as the shell, though so minute, is very 

 persistent in its forms, I have ventured to give it the above specific description " (Moore). 



This shell is so extremely minute that its real characters can be scarcely defined, and 

 I had great trouble in making the new drawings in the accompanying plate, those given 

 in ' The Geologist' not being quite correct. I cannot feel certain that it belongs to the 

 genus Thecidium. The largest specimen that has passed through my hands did not 

 exceed the fifth of a line in length and something less in breadth. 



49. Thecidium Moorei, Dav. Dav., Ool. Mon., p. 13, PI. I, fig. 10. 



Thecidea Moorei, E. Desl. Memoires sur les genres Leptsena et Thecidea des Ter- 

 rains Jurassiques du Calvados, Mem. Soc. Linn, de 

 Normandie, vol. ix. pi. xiii, figs. 9, 10, and pi. xi, 

 fig. 10, 1853. 



This species, according to Mr. R. Tate, occurs in the zone of Am. angulatus (Lower 

 Lias), in the zones of Am. margaritatus, and Am. spinatus (Middle Lias), and in the zone 

 of Am. bifrons (Upper Lias). The first specimens of the species were found by Mr. C. 

 Moore in the Middle Lias near Uminster, and subsequently by Mr. E. Deslongchamps in 

 the Lias of May, near Caen, France. 



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