Fig. 11. This Is a very abundant Spatangus or heart-shaped echinite, (_Spatangus cor marinum_, of Parkinson; _Cor testudinarium,_ of Goldfuss; _Micraster cor anguinum_, of Agassiz,) in the chalk of Kent, and some parts of Sussex. Siliceous casts, forming cordiform flints, with deep imprints of the pentapetalous rays on the vertex, are common among the stones of the ploughed fields of the Downs. Fig. 12. A _Spatangite_, (_Spatangus_ (_Micraster_, of Agassiz) _lacunosus_, of Parkinson), from tertiary strata, Malta, [Illustration: Plate LVI.] PLATE LVI. Echinites and Echinital Spines. Fig. 1. A fragment of the shell of a Turban Echinite, with three clavated or club-shaped spines attached, on chalk, from Kent (_Cidaris claviger_, of König). The inner surface of the fragment of shell is exposed. Fig. 2. A crushed shell of an elegant species of Turban Echinite (_Cidaris sceptrifera_, of Mantell), on a block of chalk; with two displaced spines near it. The sceptre-like form of the spines suggested the specific name. The chalk has been carefully cut away so as to display the shell and spines as much as possible without detaching them. From Sussex; common in the chalk near Gravesend. Fig. 3. Part of the shell, with two spines of another species (_Cidaris vesiculosus_, of Goldfuss), from Kent. Fig. 4. "A fossil echinital spine resembling a belemnite."--_Mr. Parkinson._ I am unable to determine either the species or locality of this fossil: it is indeed doubtful whether it is a spine of an echinus. Figs. 5 to 19, represent various kinds of echinital spines of Turban Echinites or Cidarites. Fig. 5. "A fossil spine named '_Bacolo di Santo Paulo_,' by Scilla."--_Mr. Parkinson._ From Verona. Figs. 6, 8, 9, 10, 11, 14, 15, 16, 17, & 18, are, I believe, referable to various species of Cidaris that occur in the Oolite or Jurassic deposits. Figs. 9 and 11. Species of _Cidaris glandiferus_, of Goldfuss. Fig. 15, is a well known form, which occurs in thousands in the Oolite Limestone, the Coral Rag, of Caen, and other localities in Wiltshire; it belongs to a beautiful Cidarite (_Cidaris Blumenbachii_[51]), which is occasionally found with similar spines attached. [Footnote 51: See Wonders of Geology, vol. ii. p. 500, figs. 3 and 6.] Fig. 12. "A flat serrated spine from Verona."--_Mr. Parkinson._ It belongs to the _Cidaris Schmidelii_, of Goldfuss.