METOPASTER ZONATUS. 45 
to have been obtained from the Upper Chalk of Kent, but no indication of locality 
is now preserved on the label. The example belonging to the Museum of 
Practical Geology is from the Upper Chalk of Gravesend. 
History.—The type of this species, which was described by Forbes in his 
memoir ‘On the Asteriade found fossil in British Strata’ (‘ Mem. Geol. Surv.,’ 
vol. 11, p. 473, 1848), originally formed part of Dr. Bowerbank’s Collection, and 
was first figured by Forbes in Dixon’s ‘Geology and Fossils of the Tertiary and 
Cretaceous Formations of Sussex,’ London, 1850, pl. xxi, fig. 4. That specimen 
is now preserved in the British Museum, where it bears the register number 
‘*H 2578.” An accurate drawing of the type is given on Pl. XVI, fig. 1 a, of the 
present work. 
4, Merropaster zonatus, Sladen. Pl. XII, figs. 2 a—2 c. 
Body of small or medium size. General form depressed. Abactinal surface in 
the fossil condition, as at present known, essentially concave in consequence of 
the conspicuously upturned extremities of the rays. Actinal surface conformably 
convex. Marginal contour pentagonal, with the radial angles slightly produced 
and obtusely rounded, and the sides distinctly lunate. The major radius measures 
nearly one-half more than the minor radius, or in the proportion of 3:2 approxi- 
mately ; the actual dimensions in the example under notice being R = 27 mm., 
r= 19 mm. approximately. Margin very thick in relation to the size of the disk, 
and regularly 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 surface of the disk, of uniform breadth 
throughout, which measures about 8 mm. at the median interradial line, in an 
example whose minor radius measures 19 mm. Excepting the ultimate paired 
plate all the supero-marginal plates are subequal, the breadth being nearly three 
times the length, the actual measurements in the example under notice being 
length 2°75—3 mm.,and breadth about 8 mm. The abactinal surface of the plates 
is distinctly convex along the median line of breadth, by which means each plate 
is conspicuously defined. The general surface of the whole supero-marginal 
series between the two ultimate plates is regularly rounded, and forms an uninter- 
7 
