30 THE BRITISH CONULARIiE. 



Horizon and Locality. — Upper Ludlow : River Esk below Henshaw Burn. 

 Type. — Geological Survey Museum, Edinburgh (reg. no. 4623). 



Section TIT.—( '. 1 N( 'ELLA TJE. 



Ornamentation cancellated, with coarser transverse main ridges, forming 

 obtuse angles across the faces, and finer and lower longitudinal ridges connecting 

 the former. Ornamentation visible to naked eye. 



(a) Transverse section square. Longitudinal ridges feeble and inconstant. 



(i) Ridges coarse, irregular, almost horizontal. Central facial groove 

 strong. G. elongata, Portlock. 



(ii) Shell small ; ridges and tubercles fine ; longitudinal ridges chiefly 

 marked on either side of the marginal grooves. 



( '. plicata, sp. now 



(iii) Shell large; ridges and tubercles very coarse; marginal grooves 



very wide and shallow. G. crassa, sp. nov. 



(iv) Marginal grooves with rounded base and prominent, smooth, rounded 



edges. C. sp. 



(h) Transverse section rhombic or elliptical. 



(a) Longitudinal ridges faint and inconstant ; tapering more rapid at 



the apex. 



(i) Facial groove well marked, often sub-central ; average angle of 



ridges 130°. Ridges fall more sharply to the " lateral " 



than to the " central " marginal grooves. G. subtilis, Salter. 



(ii) Sides nearly parallel towards the aperture ; cross-section 



elliptical; facial groove absent; average angle of ridges 150°. 



G. convplanata, sp. nov. 

 (/*) Longitudinal ridges strongly marked over the whole shell. 



(i) Shell small ; apical angle of face 17° — 20°; apical septa flat; 

 ridges nearly horizontal across the " central " marginal 

 groove, bent down sharply to the "lateral" grooves; longitu- 

 dinal bars separated. G. planiseptata, sp. nov. 

 (ii) Shell of medium size; apical angle of face 10° — 11°; apical 

 septa convex ; ridges meet at an angle in the marginal 

 grooves ; transverse and longitudinal bars prominent, and 

 equally spaced. G. vesicularis, sp. nov. 

 (iii) Shell large; apical angle of face 10° — 12°; apical septa 

 convex ; ridges nearly horizontal across the central marginal 

 groove ; the longitudinal ridges twice as numerous as the 

 transverse, rounded and in contact laterally. 



C. sowerbyi, de Verneuil. 



