110 THE FOSSIL ECHINOIDEA 



the pores of a pair united by a faint but distinct groove, which is further emphasized 

 by the presence of a thin elevated ridge separating the neighbouring pairs. The outer 

 pores are more elongate or pyriform than the inner ones; and there are 14 or 15 

 pairs of pores opposite to one of the largest interambulacral plates at the ambitus. 

 The interporiferous areas are narrow, and are furnished with two rows of minute mam- 

 millated miliary tubercles, placed at the extreme margins of the area, the space between 

 being occupied by very minute miliary granules, regularly arranged, there being at 

 the ambitus, in full-sized specimens, six granules on each plate, placed in two horizontal 

 rows of three accompanying and on the inner side of each of the mammillated granules 

 above mentioned. Towards the extremities of the area the interior series of granules 

 diminish in number, until at the very apex not more than one or two stand between 

 the outer marginal series, which latter are continuous from apex to peristome. 

 Similarly in small-sized specimens there may not be more than four of the interior 

 granules on each plate even at the ambitus, and midway between that and the 

 extremities not more than two ; the idea of two horizontal lines accompanying each 

 mammillated ambulacral granule being maintained all through, even towards the apex, 

 by the elongation of the granules transversely. 



The interambulacral areas are rather more than four times the width of the 

 ambulacra at their widest part, and there are two rows of seven or eight primary 

 tubercles in each interambulacrum. The primary tubercles are of small elevation, 

 perforate, and not crenulate ; and their mamelons are comparatively large, having the 

 edge bevelled rather than rounded. The scrobicules are wide, circular, and extend 

 close up to the edge of the plate bordering on the poriferous zone. The scrobicular 

 ring is complete, composed of 16 or 17 moderately developed, mammillated granules, 

 and touches the edge of the plate which borders on the poriferous zone, as well as the 

 actinal and abactinal margins of the plate. There are in consequence on the poriferous 

 side of the plate only a few small miliary granules occupying the upper and the lower 

 corners of the plates. The miliary zone, on the other hand, is remarkably wide, and 

 is slightly impressed along the zigzag median suture ; it is occupied by a fine, uniform, 

 miliary granulation, regularly arranged in transverse parallel lines, which extend in 

 gentle curves across the plate, and are continued in uninterrupted series from one 

 plate on to the adjacent plate of the neighbouring column. Slight superficial furrows 

 run between every two or three lines of granules, thus marking ofi" the miliary zone 

 into gently curved bands of granules, which extend from the scrobicular ring of one 

 tubercle to that of the two neighbouring scrobicules in the companion column, the 

 extremities of each band being closed by one of the mammillated granules of the 

 scrobicular ring. 



Peristome subcircular, small, 13 millim. in diameter in a specimen 35 millim. in 

 diameter at the ambitus, and 13*5 millim. in another of 37 millim. at the ambitus. 

 Apical disk subpentagonal and rather larger than the peristome. Details of the 

 apical system unknown. On one of the fragments of this Cidarid a portion of a spine 

 is attached, of which a drawing is given in fig. 7 ; it is altogether unlike any of the 

 spines we have received from the Eanikot series. 



