Fig. 5. Part of the case of a Cidaris attached to a flint by its outer surface, surrounded by upwards of twenty spines; the interior of the shell, of a light pink colour, is exposed. This exquisite fossil is now in the cabinet of the Marquess of Northampton. It was purchased by Mr. Parkinson for the sum of twenty guineas; but this was in the palmy days of the study of organic remains, before the terms Geology and Palæontology were invented, and when a choice relic of "a former world" was cheap at any price, in the opinion of the enthusiastic collector. Fig. 6. A Turban Echinite (_Cidaris_ (_Hemicidaris_, of Agassiz) _crenularis_, of Lamarck): from the Coral Rag of Wiltshire. Fig. 7. A siliceous cast--that is, a flint that has been moulded in the interior of the shell, and received the impress of the internal structure--of "_Cidaris corollaris_," of Parkinson; (_Cyphosoma correlare_, of Agassiz): from Sussex. Fig. 8. Cidaris with spines, from the Oolite of Stonesfield. Fig. 9. A specimen of one of the Cidares with large tubercles (_Cidaris coronatus_, of Goldfuss); from the Coral Rag, Oxfordshire. Fig. 10. An elegant chalk echinus (_Cidaris Königi_, of Mantell;[50] _Cyphosoma Milleri_, of Agassiz; _C. granulosus_, of Goldfuss): from Kent. [Footnote 50: Fossils of the South Downs, p. 189. (1822.)] Fig. 11. A fine species from the chalk at Gravesend (_Cidaris vesiculosus_, of Goldfuss). Fig. 12. A peculiar type of Cidaris (_Salenia scutigera_, of Goldfuss), from the freestone or upper greensand of Warminster, Wilts. Fig. 13. Another species of the same genus (_Salenia stellulata_, of Agassiz); from Warminster. Fig. 14. An enlarged view of part of the structure around the vertex of fig. 13. Fig. 15. A species of Feather-star (_Comatula pectinata_, of Goldfuss); from Solenhofen. Figs. 17, 18, 19, 20. "Minute _Stellitæ_ (that is, fossil Star-fish); from Verona."--_Mr. Parkinson._ These are probably the bodies or disks of _Ophiuræ_ deprived of their arms. Fig. 16. The nature of the specimen figured is unknown to me. [Illustration: Plate LIV.] PLATE LIV. Various Species of Fossil Sea-Urchins. Fig. 1. A large, discoidal echinite, of the type called _Clypeus_ or _Shield-echinus_, (_Clypeus sinuatus_, of Leske,) from the Coral Rag of Oxfordshire. This species abounds in the beds of this division of the Oolite in Berkshire, Wiltshire, Gloustershire, &c. Fig. 2. "_Echinanthites orbicularis_ (_Pygurus_) of Leske."--Mr. Parkinson. Fig. 3. An imperfect flint cast of an echinus (_Discoidea_), from the South Downs.