12 FOSSIL ASTEROIDEA. 



3. Calliderma latum, Forbes, sp. PL II, figs. 1 a — 1 e, 2 a — 2 d ; PI. Ill, 



figs. 1 a — 1 e, 2 a, 2b, S a, B b. 



GoNiASTEE (Asteogonitjm) latus, Forhes, 1848. Memoirs of the Geological 



Survey of Great Britain, vol. ii, 

 p. 474. 



— — — — 1850. In Dixon's Geology and 



Possils of the Tertiary and Creta- 

 ceous Formations of Sussex, 

 London, 4to., p. .333, pi. xxiii, 

 figs. 4, 5. 



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



2nd ed., p. 80. 

 AsTEOGONiTTM LATUM, Dujardin and Hupe, 1862. Hist. Nat. Zooph. 



Echin. (Suites a Buffon), p. 399. 

 GoNiASTEE (Asteogonitjm) latus, Forhes, 1878. In Dixon's Geology of Sussex 



(new edition, Jones), p. 367, 



pi. xxvi, figs. 4, 5. 



Body of large or moderate size. General form depressed. Abactinal surface 

 probably capable of some degree of inflation. Actinal surface flat. Marginal 

 contour stellato-pentagonal, the major radius probably not exceeding the minor 

 radius by more than one half. Rays narrow at the base, short, not greatly pro- 

 duced, and probably tapered to a pointed extremity. Interbrachial arcs very 

 wide and flattened, which gives a strongly marked pentagonal outline to the disk. 

 Margin of uniform thickness. 



The infero-marginal plates are more than sixteen in number, counting from the 

 median interradial line to the extremity (the tip of the ray being broken in all the 

 specimens examined). They form a remarkably broad margin to the actinal area of 

 the disk, which diminishes rather rapidly in width at the base of the rays, and then 

 slightly to the extremity. The largest infero-marginal plates near the median 

 interradial line measure about 13 mm. in breadth and 45 mm. in length. The 

 length is nearly uniform throughout, or at any rate till well out on the free part 

 of the ray ; but the breadth diminishes until the plates at the base of the ray are 

 6*5 mm., and the diminution proceeds to a certain extent along the ray. The 

 infero-marginal plates are slightly convex along their line of breadth, by which 

 means the separate plates are distinctly marked. They are well rounded at the 

 junction of the actinal and lateral surfaces, and are slightly tumid in the margin. 

 The outline of their inner or adcentral edge is also rounded. The height of the 



