CKICK : SPECIES OF NAUTILUS FEOM THE INTEEIOK OOLITE. 



131 



inflated form) slightly convex, sometimes (i.e. in the more inflated 

 form) flattened or even slightly concave, particularly on the body- 

 chamber, passing imperceptibly into the sides ; sides feebly convex ; 

 inner area almost perpendicular to the plane of symmetry of the shell, 

 well-defined from the lateral area by a subangular ridge. Body-- 

 chamber occupying about one-third of the outer whorl; aperture with 

 a wide and deep hyponomic sinus. Chambers not very deep, about 

 ten in the last half whorl of the septate part, at the centre of the 

 periphery not quite one-half of the corresponding height of the whorl 



Fig. X. — Nautilus extercbratus, n sp. a, lateral view of an example of the more 

 inflated form ; b, front view of the same. Inferior Oolite : Eradtord Abbas, 

 Dorset. Drawn from an example in the British Museum Collection [C. 3245]. 

 About two-thirds natural size. 



in depth ; septa feebly concave ; suture -line with a simple shallow 

 curve on the lateral area, almost straight on the periphery. 

 Siphuncle not seen. Test rather thick, much thicker at the 

 umbilical margin, with apparently smooth surface, or with only very 

 faint lines of growth. 

 Dimensions. 



Diameter 



Height of outer whorl 

 Height of outer whorl above \ 

 preceding whorl j 



Thickness 

 Width of umbilicus 



Greatest width of periphery ...about 58 



Remarlcs. — There are two examples of this species in the British. 

 Museum Collection (Nos. C. 3245 and C. 4498) ; their dimensions are- 



(i) 



96 mm. 



(ii) 

 123 mm. 



53 ,, 



68 „ 



36 ,, 



43 „ 



73 „ 

 12-5 ,, 



95 „ 



58 „ j 



imperfectly 

 detined. 



