Benton, M.J. and Harper, D.A.T. (1997) Basic Palaeontology, 1st edition. Prentice Hall, pp 131-143.
Clarkson, E.N.K. (1998) Invertebrate Palaeontology and Evolution, 4th edition. Blackwell Science Ltd, pp. 262-285.
Picton, B.E. (1993) A Field Guide to the Shallow-water Echinoderms of the British Isles, 1st edition, Immel Publishing, pp. 54-65.
Smith, A.B. (1984a) Echinoid Palaeobiology, 1st edition. George Allen & Unwin (Publishers) Ltd, London.
Smith, A.B. (1984b) Classification of the Echinodermata. Palaeobiology, 27, 431-459.
Smith, A.B. and Hollingworth, N.T.J. (1990) Tooth structure and phylogeny of the Upper Permian echinoid Miocidaris keyserlingi. Proceedings of the Yorkshire Geological Society, 48, 47-60.
Sprinkle, J. and Kier, P.M. (1987) Phylum Echinodermata. In R.S. Boardman, A.H. Cheetham and A.J. Rowell (eds) Fossil Invertebrates. Blackwell Scientific Publications, Oxford, pp. 550-661.
Bernard Picton was very kind in letting me use the images from his book - further lovely pictures of flora and fauna, particularly around Ireland (and with a very good section of echinoids) are available at Habitas Online, The website of the Ulster Museum Sciences Division to which Bernard belongs, and at Bernard Picton's homepage.
'The Echinoid Directory' of the Natural History Museum gives a particularly good overview of the echinoids at both basic and more complex level, and in addition provides an online taxonomic resource for the scientific community.
Further useful sites include the virtual Echinoderm newsletter, reached through links from the Smithsonian National Museum of Natural History - Invertebrate Section. and a comprehensive list of echinoderm, researcher and image links on the site of the California Academy of Sciences.