65 



CIRRUS tabulatus. 



TAB. DCXXXVIII. 



Spec. Char. Spire conical ; in the old shell the 

 latter whorls are more expanded, strongly 

 marked by lines of growth ; upper part of 

 each whorl flat or somewhat concave, bounded 

 by an obtuse, uneven keel, the lower part 

 rounded; umbihcus very large; aperture sub- 

 orbicular, truncated above ; heig-ht less than 

 the width. 



Syn. Cirrus tabulatus, Phill. Geol. Yorks. 225. 

 pi. 13./. 7. Morris, Catal. 142. Griffiths, 

 Notice of Fossils of Mount. Lime. 20. 

 Cirrus euomphaloides, Griffiths as above, 20. 

 and pi. 7.fA. 



A RATHER rugged-looking shell, distinguished from Euom- 

 phalus pentaiigulatus, M. C. t. 45, by its conical form, rough 

 surface, and great size, for it sometimes reaches a foot in 

 diameter. There is a peculiarity in its structure arising 

 from its mode of growth : additions to the shell are made 

 by thin layers, which are very thin where they line the tube, 

 but instead of being continued far beyond the aperture 

 to add to the length of the whorl, they are reflected against 

 the edge of the lip, and at the same time much thickened, 

 so that it is by the added thickness of each coat only, which 

 however is considerable, that the increase of the lip takes 

 place ; as the layers are composed of fibres arranged per- 

 pendicularly to their planes, a section of the shell across the 

 axis shows these fibres nearly parallel to its surface, or 



