48 



BRITISH BELEMNITES. 



Localities. In Middle Lias (marlstone), at Tilton-on-the-Hill, Liecestershire ; Cay- 

 thorp, in Lincolnshire, Belvoir Castle, and Oakham {Phillips). In Middle Lias (marl- 

 stone), Ilminster {Moore). In Middle Lias (marlstone), Staithes, Yorkshire [Phillips). 



Observations. The history of this interesting Belemnite is contained in specimens 

 from the marlstone and Upper Lias, to which, as far as yet appears, its geological 

 period is limited. Voltz, indeed, quotes a specimen from OoHte near Caen. The British 

 localities are almost exclusively in marlstone ; the foreign stations include Upper Lias, in 

 Wurtemburg. Variations are sensible in the guard, in regard to the transverse section, 

 which is sometimes a little compressed ; the general figure, which is occasionally a little 

 swollen towards the apex, and sometimes bent upwards ; and the terminal grooves and 

 striae, which latter on the dorsal and ventral faces are sometimes distinct and sometimes 

 wholly wanting. Occasionally there are several of these, and in this case they may be 

 due to decomposition of the laminae. The lateral grooves are always short, and usually 

 very distinct. In the interior the axis of the guard is more or less excentric than the 

 proportions given above. The sides of the phragmocone, if not quite straight, as Yoltz 



DIAGRAM 19. 



affirms, are nearer to straightness than is usual when the axis is excentric. In D'Orbigny's 

 fig. 5, the phragmocone is more incurved than is at all usual. Natm*al sections lengthways 

 of this Belemnite are rather frequent in the ventro-dorsal plane, which, near the apex, is 

 sometimes marked by a real fissure. 



Mr. Moore's large collection of these Ilminster Belemnites contains phragmocones in 

 difierent conditions of exposure, from which several facts of interest can be gathered, 

 as the accompanying diagrams (19, 20) may show. 



