PLATE XXII. 



Zone of Arietites obtusus. 



Fig. 1 . Arietites stellaris, Sowerby. Side view, natural size. British Museum. 



2. — — — Sipkonai area, with keel, channels, and skell 



structure. 



3. — — — Another specimen, showing lobe-lines in situ. 



4. — — — Front view of same fossil. 



5. — — — Siphonal area of same fossil. 



6. — — — Lobe-lines, lobes, and saddles magnified. 



The fossil shells figured in this plate all belong to the Sowerbian type collection in 

 the British Museum. The smaller specimens (figs. 3, 4, 5, and 6) were those figured in 

 the * Mineral Conchology,' and are specially marked with Sowerby's green ticket. 



