MITRASTER HUNTERI. 59 
1. Mirraster Hunveri, Forbes, sp. Pl. IX, figs. 3a—3e; Pl. XII, figs. 3a—3e; 
Pl. XV, figs. 3a—sd b. 
GONIASTER REGULARIS, Mantell, 1844. Medals of Creation, vol. i, 
p. 335, lign. 73 (non Linck). 
GontasteR (Gonropiscus) Hunrert, Forbes, 1848. Memoirs of the Geological 
Survey of Great Britain, vol. i, 
p. 471. 
= == _ Forbes, 1850. In Dixon’s Geology and 
Fossils of the Tertiary and Creta- 
ceous Formations of Sussex, 
London, 4to, p. 331, pl. xxi, fig. 1. 
—_ — — Morris, 1854. Catalogue of British Fossils, 
2nd ed., p. 81. 
Astroconium HunrTert, Dujardin and Hupé, 1862. Hist. Nat. 
Zooph. Echin. (Suites 4 Buffon), 
p- 399. 
GontrasTER (Gontopiscus) Huntert, Forbes, 1878. In Dixon’s Geology of Sussex 
(new edition, Jones), p. 9365, 
pl. xxiv, fig. 1. 
Body of small size. General form depressed. Abactinal surface flat and 
apparently depressed within the boundary of the supero-marginal plates, the 
gibbosity of the latter and their centrally sloping surface giving a concave character 
to the area generally in fossil examples, which was probably always more or less 
present. Actinal surface flat or with a tendency to be slightly convex. Marginal 
contour subcircularly pentagonoid, the sides being slightly convex or bulging out- 
ward. The major radius is proportional to the minor radius as 100 : 90°47 approxi- 
mately ; and the rays are not produced, the angles of the pentagon being obtusely 
rounded. Margin thick and well rounded, the slope being more gradual on the 
actinal surface. 
The supero-marginal plates are three in number counting from the median 
interradial line to the extremity, or six from the tip of one ray to the tip of the 
adjacent ray, exclusive of the odd terminal or “‘ ocular” plate in each case. They 
form a broad border to the abactinal area of the disk, of uniform breadth through- 
out, which measures about 6°3 mm. at the median interradial line in an example 
whose diameter (R + 7) measures about 40 mm. Excepting the ultimate plates 
all the supero-marginal plates are of equal size and uniform, the breadth being 
a little more than once and a half the length, the actual measurements in the 
