32 FOSSIL ASTEROIDEA. 
GontasTER (Gonropiscus) ParKinson1, Forbes, 1848. Memoirs of the Geological 
Survey of Great Britain, vol. ii, 
p- 472. 
_ — RECTILINEUS, McOoy, 1848. Ann. and Mag. Nat. 
Hist., ser. 2, vol. ii, p. 408. 
— — Parxkrnsoni, Forbes, 1850. In Dixon’s Geology and 
Fossils of the Tertiary and Cre- 
taceous Formations of Sussex, 
London, 4to, p. 332, pl. xxi, 
figs. 10, 11; pl. xxii, figs. 5—7. 
= = _— Morris, 1854. Catalogue of British 
Fossils, 2nd ed., p. 81. 
— —_— RECTILINEUS, McCoy, 1854. Contrib. Brit. Pal., p. 55. 
— — —_— Morris, 1854. Catalogue of British 
Fossils, 2nd ed., p. 81. 
AsTROGONIUM PaRKINSONI, Dujardin and Hupé, 1862. Hist. Nat. 
Zooph. Kchin, (Suites 4 Buffon), 
p. 399. 
_— RECTILINEUM, Dujardin and Hupé, 1862. Ibid., p. 400. 
GonrasTER (Gonropiscus) Parxrnsont, Forbes, 1878. In Dixon’s Geology of 
Sussex (new edition, Jones), 
p: 365, pl. xxiv, fies: TOs 
pl. xxv, figs. 5—7. 
PENTAGONASTER REOCTILINEUS, Woods, 1891. Catalogue of the Type 
Fossils in the Woodwardian 
Museum, Cambridge, p. 36. 
Body of medium size. General form depressed. Abactinal surface flat, with 
a tendency, however, for the extremity of the rays to be slightly upturned; as 
found in the fossil state the area occupied by the abactinal plates is usually at a 
lower level than the marginal plates, which leads to the assumption that the 
abactinal floor had collapsed or fallen to a certain extent on the death of the 
animal. Actinal surface slightly convex. Marginal contour pentagonal, with 
slightly lunate sides, the curvature being often flattened at right angles to the 
median interradial line. The major radius measures about one-third more than 
the minor radius, and frequently less than one-third; the rays are consequently 
very feebly produced. Margin thick and well rounded. 
The supero-marginal plates are four in number, counting from the median 
interradial line to the extremity, or eight 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 
throughout, which measures. about 9 mm. at the median interradial line in an 
example whose minor radius measures 30 mm. Excepting the ultimate paired 
plates all the supero-marginal plates are of equal size, the breadth being about 
