60 FOSSIL ASTEROIDEA. 



specimen under notice being length 4 mm. and breadth 6*3 mm., in the plate 

 adjacent to the median interradial line. The length of the plate at the end which 

 falls in the margin of the disk is a shade greater than the adcentral or inner end, 

 and the plates are consequently faintly wedge-shaped, but so slightly that the 

 character is scarcely noticed at first sight. The ultimate plates, however, are 

 distinctly wedge-shaped, the length at the outer margin being a little greater 

 than that of the other marginal plates, while the length of the inner end is rather 

 less — often not more than one-half the lens^th of the same end in the other plates. 

 The breadth of the ultimate plates is the same as that of all the supero-marginal 

 plates ; and the corresponding plates of the two adjacent sides touch one another 

 throughout, the line of junction falling in the median line of the ray. The abactinal 

 surface of the plates is distinctly convex, and the character is more conspicuously 

 emphasised by the plate becoming rapidly gibbous on the outer half, the outer 

 side of the eminence forming the rapid bend to the lateral wall of the plate. 

 The height of the plates as seen in the margin is usually equal to, or even 

 rather greater than their length, but may occasionally be less. There is no 

 diminution in height as the plates approach the extremity of the ray, and the 

 ultimate paired plate has a tendency to appear even a trifle higher and more 

 gibbous than the others, but the character is derived probably more from the 

 position in which the plate sometimes is than fi'om an actual increase in size or 

 gibbosity. The abactinal surface of the plates is covered with coarse tuberculiform 

 mammillations which gradually die out before reaching the apex of the gibbosity. 

 In the interspaces between the eminences are small, more or less widely spaced 

 punctations, and these extend over the whole surface of the plate, and are 

 consequently present on the outer portions as well as on the lateral wall. There 

 is a narrow depressed border round the entire margin of the plate, which is very 

 minutely punctate (see PI. XII, fig. 3 c). In smaller examples there often appears 

 to be only one or two rows of punctations. The ornamentation of the ultimate 

 paired plates is precisely similar to that on the other supero-marginal plates. 



The odd terminal or " ocular" plate is very small, and, so far as I can make 

 out, resembles superficially a short truncated cylinder which protrudes somewhat 

 cannon-like from a small triangular space left by the ultimate paired plates similar 

 to what I have already described in Metopader. 



The abactinal area of the disk within the boundaiy of the marginal plates is 

 covered with comparatively large polygonal plates, with closely crowded, rather 

 coarse, uniform granulations, upon which miliary granules or spinelets were 

 previously borne. The primary apical plates are remarkably large, and the plates 

 in the interradial areas are larger than the plates in the radial areas. Of the 

 plates in the radial areas at least the median series and two series on each side 

 have bases of a six-rayed, substellate form. These are admirably seen in an 



