Nautiloidea. 29 



been found in Great Britain and Belgium. There is usually a large Nautilidae. 



vacuity in the centre of the shell, the innermost portion of the GALLERY 



shell being sometimes out of contact with the adjacent whorl' ,, 



° ** ' Table-case 



71. 



Fig. 51. — Discites nwtabilis, M'Coy. Carboniferous Limestone : Ireland. 



the inner whorls are often richly ornamented, the older whorls 

 having usually merely transverse lines of growth. Some species 



Fig. 52. — Coelonautilus multicarinatus, Sby. Carboniferous Limestone: Ireland. 



have also spiral sulci, but these spiral ornaments are much more 

 prominent in Coelonautilus (Fig. 52), which ranges from the Car- 

 boniferous to the Trias. 



