PLATE XIII. 



Opalinnm-zone. 

 Figs. 1 — 10. — Lioceras opalinum (Beinecke). 



Fig. 1. — Side view of a typical large specimen, with almost the whole of the 

 body-chamber present, and with the test extremely well preserved. Haresfield 

 Hill, Gloucestershire. My Collection. (Page 35.) 



Fig. 2. — Front view of the same specimen, showing the almost complete 

 absence of a carina, and also the rounded ventral area of the body-chamber. 



Fig. 3. — Side view of a portion of a large specimen, five and a half inches in 

 diameter, to show the termination to the body-chamber. Haresfield Hill. My 

 Collection. (Page 36.) 



Fig. 4. — Side view of a small typical specimen (to compare with Reinecke's 

 figure). Coaley "Wood, Gloucestershire. My collection. (Page 36.) 



Fig. 5. — Front view of the same specimen, showing that the carina is slightly 

 more developed in youth. 



Fig. 6. — Side view of a very small specimen. Burton Bradstock, Dorset. My 

 Collection. (Page 36.) 



Fig. 7. Side view of a somewhat compressed variety with wider umbilicus and 

 more sloping inner margin. Only a portion of the body-chamber is present, as 

 shown by the X. Haresfield Hill. My Collection. (Page 39.) 



Fig. 8. — Front view of the same specimen. The upper portion of the last 

 whorl has the test off, and shows a peculiarly compressed section. 



Fig. 9. — Side view of a younger specimen of the more widely centred variety. 

 Haresfield Hill. My Collection. (Page 39.) 



Fig. 10. — Front view of the same. 



Lioceras opalinum, var. comptum (Beineche). 



Fig. 11. — Side view of a very young specimen (to compare with Reinecke's 

 figure, and also with fig. 6). The test is absent and the strise are consequently 

 more prominent. Burton Bradstock. My Collection. (Page 55.) 



Intermediate form. 



Fig. 12. — Portion of a variety between Lioc. opalinum and comptum, showing 

 the commencement of the lateral process to the termination, which the young shells 

 possess. Burton Bradstock. My Collection. (Page 54.) 



