162 GUIDE TO THE FOSSIL INVEETEBEATE ANIMALS. 



Gallery has three or four whorls closely coiled in one plane. The 

 'aWe-case Ordovician and Silurian rocks of Bohemia furnish several 

 2. specimens of a flat closely coiled shell, called Barrandeoceras, 



after the great palaeontologist of Bohemia ; an example from 



Dudley is also shown. 



c 



Fig. 92. — Palaeozoic Nautiloidea. a, Ophidioceras simplex, Silurian, 

 Bohemia, b, Hercoceras mirum, Devonian, Bohemia, c, Apheleceras 

 7nutahile, and d, Vestinautilus multicarinatus, Carboniferous Lime- 

 stone, Ireland. All slightly less than natural size. (From Foord.) 



The coiled cone of the preceding shells is generally 

 circular or elliptical in section, and has a smooth or slightly 

 ornamented surface. There are others in which the cone is 

 flattened or grooved, and the surface bears more marked 

 ornament. Thus Trigotioceras, found in tlie Carboniferous 



