METOPASTER BOWERBANKII. 43 
the extremity of the ray, and the ultimate paired plate is not prominent or gibbous 
abactinally. The whole superficies of the supero-marginal plates is covered with 
small, widely spaced, equidistant, uniform punctations, and along the entire 
_ margin of the plate is a very narrow and deeply depressed border of fairly 
uniform breadth, covered with much smaller and closely crowded punctations, 
upon which much smaller granules than those which occupied the central area of 
the plate were originally borne. One or two or even three small entrenched 
pedicellariza may be present on the central area of a plate, irregularly 
disposed. 
The ultimate paired plate is triangular in form as seen from above. The 
margin or side which represents its length and coincides with the margin of the 
disk measures a little more than once and a half or nearly twice the length of the 
adjacent supero-marginal plates; and the margin representing the breadth of the 
plate which abuts on the penultimate supero-marginal plate is shorter than the 
margin of the latter plate. The remaining side of the plate which touches the 
corresponding ultimate plate of the adjacent side of the disk, and falls in the 
median radial line of the disk, is subequal to or even slightly shorter than the 
breadth of the preceding marginal plates. The ultimate plate in this species is 
not elongated, and no prolongation beyond the normal pentagonal contour of the 
disk occurs in the extension of the median radial line. The surface of the ultimate 
plate is covered with punctations and margined with a finer and closely crowded 
series precisely similar to those on the other supero-marginal plates. 
The abactinal area of the disk within the boundary of the marginal plates is 
covered with small, subregular, hexagonal plates or paxillar tabule, which have 
their surface marked with minute, low, subhemispherical, and closely placed 
miliary granulations, which do not, however, extend quite to the margins of the 
plates. A number of the plates bear in the centre a rather large entrenched 
pedicellaria, consisting of a central foramen and normally two lateral fosse, and 
there is usually a circular series of coalesced granules in which the fosse are 
included, which imparts a very characteristic appearance to the organ in this 
species (see Pl. XVI, fig. 1d). ; 
The following description of the characters of the actinal area of the disk of 
this species is taken from an example preserved in the Museum of Practical 
Geology, Jermyn Street, and figures of which are given on Pl. XV, figs. 2a—2d. 
The infero-marginal plates are eight in number counting from the median 
interradial line to the extremity,—that is to say, there are sixteen for the whole 
side of the disk, as against ten in the supero-marginal series. The length of the 
four innermost plates on each side of the median interradial line is slightly greater 
than that of the corresponding plates of the supero-marginal series; and there 
are four infero-marginal plates much smaller than those preceding, corresponding 
