NOTES ON THE BRITISH JURASSIC BRACHIOPODA. 249 



given off at right angles near the centre of the valve, the 

 remaining portion soon after becoming reflected (8, p. 65) . 



Terebratella first made its appearance in the Oolitic rocks, 

 where it is represented by the following species : — 



T. huckmani, Moore (type in the Bath Museum), T. 

 furcata, Sow., and T. inoorei^ Dav., all three from the Great 

 Oolite of Hampton Cliff, near Bath. 



A Terehratella-\\ke shell is fonnd in the Middle Lias ; 

 it is provisionally placed in this genus as T. (?) Uasiana, 

 Desl. sp. 



Terebratella is represented in existing seas by some nine 

 to twelve or more species. Whether or not the researches 

 made by Messrs. OEhlert and Fischer on the recent Brachio- 

 poda of the Magellanian province will bring about an alter- 

 ation in the generic appellation of our Jurassic Terehratellse 

 it is difficult to say at present. They certainly have demon- 

 strated beyond the possibility of a doubt that the genera 

 Waltonia (Davidson), and Magasella (Dall), are really 

 immature Terehratellse in which the brachial apparatus has 

 not completed its development ; also that Terebratella is 

 closely related to and should precede Magellania in any 

 system of classification based on the natural evolution of 

 genera (6). 



It is only right to say that Davidson was not satisfied 

 that Magasella was a good genus ; he thought that the 

 species so referred were perhaps undeveloped forms of 

 Terebratella. 



ISMENIA, King, 1849. 



Etym. — IsmeniuSj of or belonging to Thebes. 

 Syn. — Terebratula (?), Davidson, 1884. 



Deslongchamps, w^ho made Ismenia a sub-genus of his 

 Waldheimia, described it as follows : — " Shell more or less 



s 



