PLATE XIV. 



Zone of Aegoceras planorbis. 



Fig. 1. Aegoceras planorbis, Sowerby. Side view, natural size, from Lower Lias, 

 Robin Hood's Bay. Woodwardian Museum, Cambridge. Leckenby 

 Collection. 



2. Front view, natural size, of the same specimen. 



3. Lateral view of Aegoceras planorbis, from the Lower Lias of Wiirttemberg, with 



the Aptychus and oral aperlure contraction, drawn by Dr. W. Waagen, 

 " Ueber die Ansatzstelle der Haftmuskeln beim Nautilus und den Ammoniden," 

 ' Palseontographica,' Band xvii, T. xl. 



4. Accurate outline of the dorsal and lateral lobes and saddles, enlarged. 



Zone of Aegoceras angulatwn. 



5. Aegoceras angulatdm, Schlotheim. Lateral view, natural size. Lyme 



Regis. My collection. 



6. Siphonal area showing the flexure of the ribs and angles they describe. 



