28 FOSSIL ASTEROIDEA. 



the half adjacent to the supero-marginal series (see PI. IV, fig. 4 c). I have not 

 found any pedicellai'ise on these plates. 



The adambulacral plates are broader than long, except on the outer part of 

 the ray, and bear on the surface four or five ridges with granuliform eminences, 

 upon which the spinelets constituting the adambulacral armature were originally 

 borne. In one well-preserved specimen these small articulatory tubercles are seen 

 to have each a small microscopic central puncture (see PI. IV, fig. 3 c), but I am 

 not certain whether this is always present. 



The actinal interradial areas are small, and are covered with a comparatively 

 small number of large pentagonal or tetragonal intermediate plates, which are 

 arranged in series parallel to the ambulacral furrow, and form a compact 

 tessellated pavement. The actinal intermediate plates are larger in relation to the 

 size of the disk than in the species above described. The plates of the series 

 adjacent to the adambulacral plates, and a few of the plates of the succeeding 

 series within the angle towards the mouth, are larger than the others. The 

 intermediate plates do not extend beyond the second, or at most a short distance 

 along the margin of the third infero-marginal plate, counting from the median 

 interradial line. The surface of the intermediate plates, excepting a border 

 round the margin of the plate, is covered with large punctations, which are nearly 

 confluent, and in some cases almost give the appearance of a coarse reticulate 

 superficial ornamentation ; the border round the margin of the plate above 

 mentioned is marked with a concentric crenulation (see PI. IV, fig. 3 b). Within 

 the pits are more or less definite elevations. In other examples the reticulate 

 character is less marked, and the margin of the pit is then prominently lipped, 

 and the marginal crenulation is not so strongly shown (see PI. IV, fig. 4 e). 



In the marginal view of the type specimen the supero-marginal plates are seen 

 to be higher than the infero-marginal plates, and that their height is greater than 

 their length, whereas in the infero-marginal series of plates the height is less than 

 the length (see PI. IV, fig. 2 c). 



In other examples the mouth-plates are preserved. These are rather small, 

 triangular, and covered with rather large, irregular, tuberculose eminences for 

 the attachment of the mouth-plate armature. 



Variations. — Three examples of this species are figured on Plate IV. These 

 present a number of minor differences, which will be readily noticed on referring 

 to the figures. 



The example which is shown in fig. 3 a has the marginal border of the infero- 

 marginal plates rather less bi'oad than in the type form, and it is especially 

 remai'kable for the peculiar retiform and crenulated ornamentation of the actinal 

 intermediate plates already noticed. The disposition of the armature of the 



