NATURAL HISTORY SOCIETY OF GLASGOW. 201 



a good deal crushed, and do not appear to have anything especially 

 remarkable about them. 



The radial plates, on the other hand, judging from one very well 

 preserved piece, are peculiar and characteristic. The plate in 

 question is narrowed below, along its line of junction with one of 

 the basals, and expands rapidly upwards, the lateral margins 

 parallel with one another (and those of contiguous plates placed in 

 deep grooves), forming a broadly hexagonal figure, the fore part of 

 winch forms a re-entering angle or fork, for the reception of the 

 ambulacrum. The bifurcation is wide, and extends for nearlv 

 three-fifths of the length of the plate, has elevated rim-like mar- 

 gins, and is bevelled inwards towards the ambulacrum. The apex 

 of the bifurcation, into which fits the tip of the ambulacrum, is 

 lip-like and projecting. The two foremost extremities of the fork 

 are obliquely truncated, meeting against the interradial plates. 

 From the apical projection of the fork to the base of the plate the 

 surface is obtusely angulated in the middle line, having on each 

 side an oblique radiating ridge, passing to the angles formed by 

 the union of the parallel sides with the two shorter basal edges of 

 the plate. The surface of this and the other radial plates is orna- 

 mented by a series of finely-executed lines parallel to the margins 

 of the plate, and which make, in their more or less concentric 

 course, five distinct angles, thus : — First, following the line of 

 junction of the radials and interradials at the fore part of the plate 

 on each side (2 angles); second, in crossing the two lateral 

 radiating ridges (2 angles); and third, in crossing the central 

 obtuse ridge (1 angle) = 5 angles. 



The oral plates are small, obtusely lanceolate, and do not 

 extend above the truncated summit of the calyx. They occupy 

 the angles between the halves of every two radial plates. 



The ambulacra are narrow, moderately elongated, and pointed, 

 rather deeply inserted in the radial forks, and each divided by a 

 well marked, deep, median ambulacra! groove, giving off distinct 

 branches right and left. Beyond this the component plates of the 

 ambulacra are not discernible. The central hiatus, the four 

 spiracles, and the fifth compound aperture (commonly called the 

 ovarian apertures) are quite obliterated, and the summit presents 

 no further features of interest. 



So far as the limited material at my disposal, and the state of pre- 

 servation of the same, will allow of an opinion being formed, this 



