PLATE XV. 



PlSIDIUM CASERTANUM (Poli). 



1. or, b. External aspect of a pair from the type locality, Caserta. 



2. , b. Enlargement of the Hinge of the above. 



3. a, b. Diagrammatic enlargement of the Hinge of a typical 



specimen. 



4. a, b. Enlargement of the Hinge of P. fossarinum, Clessin. 



5. a, b. Diagrammatic enlargement of the Hinge of the lake, or 



still- water form. 



6. a, b. Internal aspect of a pair of valves from Fit ton Hall. 



Oldham, Lancashire. ("P. pusillum, var. gran- 

 dis": T. Rogers coll.) 



7. . 6. of a pair from Gateshead, Durham. ("P. cinerevm": 



T. liogers coll.) 



8. a, b. of a pair from Scarborough, Yorkshire. 



9. , b. of a pair from Annadale, Co. Down. 



10. , b. of a pair from Swinton, Lancashire. ("P. fonti- 



nale, var. cinereum [sic]," marked " J. G. Jeff." : 

 T. Rogers coll.) 



11. a, b. of a pair from Manchester. ("P. fontinale, var. 



rosea, Scholtz " from 0. Boettger.) 



12. a, b. of a pair from Swinton, Lancashire. ("P. pits ilium, 



large variety, J. G. Jeff." : T. liogers coll.) 



13. a, b. - of a pair from Naples. (" P. australe, Phill." : 



11. Bellini.) 



14. , b. - of a pair from Bath, Somersetshire. ("P.fontinale, 



var. pulcheUa, named by Mr. Jenyns": T. Rogers 

 coll.) 



15. a, b. of a pair from Addington, Surrey. 



16. , b. of a pair from Sannton, Mortehoe, Devon. 



17. of a right valve from Trancailla, Italy. 



18. #, b. of a pair from Sicily. (" Galileja tenebrosa, 0. G. 



Costa " : 11. Bellini.) 



19. a-li. of a series of valves from Giesegaard, near Borup, 



Sealand. 



20. a-h. from Lyngby-Bagsvor So, Sealand. 



21. a, b. of a pair of valves from North Wootton, Norfolk. 



22. a, b. of a pair from Tudor Hill, Sutton Cold field, War- 



wickshire. 



23. , b. of a pair from Trancailla, Italy. 



*#* The scale in millimetres under each fig-ure, or series of figures, 

 shows the amount of magnification. 



