﻿CALLIDERMA MOSAICUM. 9 



found in ferric sulphide at Amberley Pit, Sussex. The fragment figured on 

 PL VIII, figs. 2 a, 2 b, 2 c, is from the Lower Chalk of Dover. 



History. — The type specimen, from which this species was originally described 

 by the late Edward Forbes in 1848, formed part of the collection of Mrs. Smith, of 

 Tunbridge Wells. It is now preserved in the British Museum. It was first 

 figured in Dixon's ' Geology and Fossils of the Tertiary and Cretaceous Forma- 

 tions of Sussex,' London, 1850. PL I of the present memoir is a faithful draw- 

 ing of the same beautiful specimen. 



2. Callidebma mosaicum, Forbes, sp. PL V, figs. 2 a — 2 e ; PL VI, figs. 1 and 2 



a, b, c; PL VII, figs. 4 a, b, c. 



Goniastee (Asteogonium) mosaicus, Forles, 1848. Memoirs of the Geological 



Survey of Great Britain, vol. ii, 

 p. 475. 



— — mosaicus, Forbes, 1850. In Dixon's Geology and 



Fossils of the Tertiary and Cre- 

 taceous Formations of Sussex, 

 London, 4to., p, 334, pi. xxiv, 

 fig. 26. 



— — mosaicus, Morris, 1854. Catalogue of British Fossils, 



2nd ed., p. 80. 

 Asteogonium mosaicum, Dujardin and Hupe, 1862. Hist. Nat. 



Zooph. Echin. (Suites a, Buffon), 



p. 399. 

 Goniastee (Asteogonium) mosaicus, Forbes, 1878. In Dixon's Geology of Sussex, 



(new edition, Jones), p. 367, 



pi. xxvii, fig. 26. 

 Goniastee mosaicus, Etheridge, 1885. In Phillips's Manual of 



Geology (new edition), part ii, 



by E. Etheridge, p. 560. 



Body of large size. Disk large. Rays narrow at the base and well produced. 

 General form depressed and thin. Abactinal area probably capable of slight 

 inflation, and more or less flexible ; some carination present in the radial abactinal 

 regions. Actinal surface flat. Marginal contour stellato-pentagonal, the major 

 radius measuring more than twice and a half the minor radius. Rays narrow, 

 the supero-marginal plates being united in the median radial line. Interbrachial 

 arcs wide and with their curvature more or less flattened, which gives a distinctly 

 pentagonal character to the disk. Margin rather thin, and with the lateral wall 

 perpendicular. 



2 



