736 
PROFESSOR WYVILLE THOMSON ON THE ECHTNOIDEA OF THE 
long. 7° 40' W., about 100 miles to the north of the Butt of the Lews. Numerous 
fragments and spines from depths from 500 to 800 fathoms otf the west coasts of Scot- 
land and Ireland. 
This form derives a special interest from its evident relation to the fossil Ecliinothuria 
floris from the White Chalk, described by the late Dr. S. P. Woodward. 
Two imperfect specimens of this singular fossil had been obtained — the first, many 
years ago, by Mr. Wickham Flower, of Park Hill, Croydon, from the Upper Chalk of 
Higham, near Rochester, and the second by the Rev. Norman Glass, from Charlton, in 
Kent. 
Mr. Flower’s specimen consisted of several series of imbricated plates converging 
towards a point, and some of them showing the characteristic double pores and spine- 
tubercles of the Echinoderms, which at once set aside the first idea that it might be part 
of a large cirriped allied to Loricula. Edtvard Forbes examined the Higham specimen, 
but was unable to come to a decision. Afterwards Dr. Woodward examined it, and felt 
in a like dilemma. The general impression was that it might be a group of the scales 
of the peristome or the periproct of some large Echinoid allied to Diadema or Cyphosorna. 
While Dr. Woodward was hesitating about publishing Mr. Flower’s specimen, the 
second example was procured by the Rev. Mr. Glass, and it seemed to solve the problem ; 
for it consisted of a well-developed dental apparatus with portions of several series of 
imbricating plates radiating from it, thus apparently supplying the peristome and lantern 
of the same great Diadema or Cypliosoma of which Mr. Flower’s specimen might be the 
apex or periproct. 
Still there were difficulties in the way of accepting this explanation. Dr. W oodward 
writes : — “ In Mr. Flower’s specimen the imperforate plates imbricate towards the centre, 
where the smaller ends of the several series converge. In Mr. Glass’s specimen they 
slope away from the centre or mouth, that is also towards the apex. The perforated or 
ambulacral plates which overlap one another outwardly in fig. 1 are seen in fig. 2 sloping 
towards the dental cone and reclining upon it. The portion of an ambulacral area 
(a, fig. 2) consists of seven plates, diminishing in size in a line not accurately directed 
towards the centre. This portion exhibits the interior surface of the plates, known by 
their curved surfaces destitute of ornamental granules ; it is not, however, the oral end 
of one of the segments turned over (a thing scarcely possible to happen), for in that case 
the dip of the plates would be reversed ; but it must be the opposite (or apical) extre- 
mity of a series folded back upon its origin and exposed to view by the damage which 
the surface of the specimen has sustained. From this circumstance it seems probable 
that the whole fossil when complete was not elongated nor even spherical, but somewhat 
depressed in a vertical direction, though doubtless admitting of a moderate degree of 
flexure. At the last hour, after making this drawing, I ventured to clear away the 
chalk from the side of Mr. Glass’s fossil, where the ambulacral segment is seen to curve 
as if it might be continued round to the other surface. The attempt was successful ; 
for the ambulacrum and also the adjacent interambulacral segment were found conti- 
