METOPASTER BOWERIUNKII. 43 



the extremity of the ray, and the ultimate paired plate is not prominent or gibbous 

 abactinally. The whole superficies of the supcro-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 l)readth, 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 

 pedicellarije 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 suporo-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 sul)equal 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 tabulae, 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 fossse, and 

 there is usually a circular series of coalesced granules in which the fossae are 

 included, which imparts a very characteristic appearance to the organ in this 

 species (see PI. XVI, fig. 1 d). 



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, Jerrayn Street, and figures of which are given on PI. XV, figs. 2n — 2(1. 



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, corresjjonding 



