34 NOTES ON THE BRITISH JURASSIC BRACHIOPODA. 



tapering into the- shape of an acute blade, to the sides of 

 whicli the adductor muscle was, no doubt, fixed (8, p. 82). 

 This septum is absent in Spirifera. 



Spiriferina may be distinguished externally from any 

 other Jurassic brachiopod by the following features: — "Well- 

 pronounced, imperforate beak ; beak - area well defined, 

 which is in most of the shells largely developed and inter- 

 rupted by a pseudo-deltidium, notched in the vicinity of the 

 cardinal edge ; also by the well-defined and strongly marked 

 hinge-line and area." 



Spiriferina first appeared in the Devonian period, reached 

 its maximum development during the Liassic epoch, and 

 appears to have died out in the Oolitic epoch. Fourteen 

 species are found in the Jurassic rocks, including S. (?) 

 rnoorei, Dav., and S. signiensis, Buv. (?) from the Lias ; 

 also S. (?) minima and oolitica, Moore, from the Inferior 

 Oolite of Dundry, vfhich are provisionally refered to this 

 genus. Most of the other species are from the Middle Lias. 



8. walcotti, Sow., is assuredly one of the most handsome 

 of the SpiriferinoB — or indeed of the Brachiopoda : from no 

 other part of the country can such fine and well preserved 

 specimens be obtained as from the Lower Lias of the Rad- 

 stock district. Two described specimens from this district 

 is located in the Bath Museum ; also types of — 



S. (?) minima, Moore, from the Inferior Oolite of Dundry. 



;S. (?) oolitica, „ „ ,, „ ,, 



S. milnsterii, Dav., from the Middle Lias of Ilminster. 



RHYNCHONELLA, Fischer de Waldheim, 1809. 



Etym. — pvyxos, a beak. 



This interesting but extremely difficult group of shells 



is so well known that it is quite unnecessary to describe in 



any detail the external shape of the shell, or its ornamentation. 



