742 
PROFESSOR WYYILLE THOMSON ON THE ECHINOIDEA OE THE 
interambulacral and the ambulacral plates, in irregular rows parallel to the rows of the 
larger spines. A long style (Plate LXVII. figs. 5 & 6) is articulated to one of the miliary 
granules. This style enlarges somewhat at the distal end ; and from the enlargement 
there spring four delicate rods which gradually widen and become tubular, their walls 
being at length perforated by wide fenestrae (Plate LXVII. fig. 6). Each rod is sur- 
mounted by a hollow disk very gracefully twisted, reminding one somewhat of a frustule 
of Campylodiscus. The walls of the disk are fenestrated, and from the margin a delicate 
calcareous border is thrown backwards and downwards, edged with a fringe of singularly 
elegant design. A large mass of red muscle, covering the end of the main stem and the 
bases of the four branches, no doubt for the purpose of imparting motion to the latter, 
renders these pedicellarise very conspicuous. They are strikingly beautiful objects, and 
differ entirely from any pedicellarise which have hitherto been described. 
The pedicellarise next in size are of the ordinary tridactyle type, with a special modi- 
fication in form, % the bases of the valves being very broad, and the spoon-shaped extre- 
mities unusually long and close-fitting (Plate LXVII. fig. 7). The third set resemble 
closely the minute pedicellarise of C. hystrix ; but they are more delicate in their propor- 
tions, corresponding in this with the test and its other appendages. 
The apical disk (Plate LXVI. figs. 1, 2) is 18 millims. in diameter from the outer 
angle of an ovarial plate to the outer edge of the ocular plate opposite. The ovarial 
plates are large, and have nearly the form of an equilateral triangle ; the outer angle, 
which is produced somewhat more than the others, is wedged between the first p&ir of 
interambulacral plates in the space formed by their common inclination towards the 
oral pole. The ovarial openings are remarkably large, 2’5 millims. in diameter, so 
large as to occupy the whole of the central part of the ovarial plate, leaving a^arrow 
rim only. Even this rim is sometimes encroached upon and the side of the plate sepa- 
rated into two parts. The ocular plates are large and mallet-shaped. A transversely 
oval portion continues the line of the upper edges of the ovarial plates, coming into 
contact with one of these on either side, while a narrower process, perforated in the 
centre by the minute ocular pore, meets the two upper plates of the ambulacral series. 
On the inside of the test a raised calcareous ridge runs continuously along the free edge 
of the ovarial plates through the ocular plates, with a suture at the points of junction, 
forming a kind of ring supporting the edge of the apical space. The madreporic tubercle 
is large, formed of the modified upper portion of one of the ovarial plates. The mem- 
brane of the periproct is supported by irregularly shaped scattered plates bearing small 
tubercles and miliary grains and small spines and pedicellariae. These plates are of 
considerable size, and are lenticular in form towards the circumference, but they become 
smaller and finally almost linear as they approach the anus. 
As in C. hystrix , a calcareous keel runs across the interambulacral spaces at the edge 
of the oral opening, and complete auriculae span the ambulacra ; but these auriculae, 
like the other part of the shell, are very light. The oral aperture is 25 millims. in dia- 
meter with an entire margin. As in the other members of the family, 'the peristomial 
