166 ECHINOIDEA. 
from their great size and the distinctness of their bright yellow 
colour from the purplish test; sometimes they may be remarkable 
for their size only, and sometimes they may be quite inconspicuous. 
The general coloration, again, varies within wide limits ; the general 
facies may be a universal purple, but it may be brown, or yellowish, 
or whitish. So, again, the form of the test is sometimes well rounded, 
sometimes flattened ; the cordiform contour may be qualified, so that 
some specimens are more truncated and some more evenly rounded 
than others. 
The ambulacral petals are wide and each of the antero-lateral pair 
s longer than the postero-lateral ; the pores in the neighbourhood 
of the apex are quite small, and the reduction in size is most marked 
and most extensive in the anterior half of the antero-lateral petals ; 
the inner pore of a pair is always smaller than the outer. Anterior 
groove rather wide. In the apical area the madreporite is very 
prominent. The mouth is wide, and the lower lip has a rounded 
angle. The subanal fasciole is well-marked, broad, with a wide and 
deep angle on the side nearer the anus. The anus is transversely 
oval, looks backwards and downwards. The tubercles vary con- 
siderably in size; the largest are found on the dorsal surface, and 
chiefly between the petals; a very few are found within the petals ; 
the granules forming the general covering of the upper surface 
of the test have a tendency to become smaller as the ambitus is 
approached. 
On the ventral surface the tubercles are generally larger; they 
are smallest near the ambitus and largest in the region of the 
mouth ; within the subanal fasciole the tubercles are smallest in the 
narrowest region and largest in the wings on either side. 
There is some not inconsiderable variation in the breadth and 
form of the petals; the postero-lateral are sometimes almost oblong 
instead of petaloid; in young specimens the pores of a pair are not 
markedly different in size; while always wide the anterior groove 
varies somewhat in depth. 
Greatest breadth of 
A 
Breadth Breadth Ant.-lat. Poste 
Length. Breadth. Height. of mouth. of vent. ambulacra. ambulacra, 
100 100 ol 20°5 16 12°5 12°5 
85 92 51 18 11 8 78 
rats) 84 48 145 12°5 12 att 
80 87 44 17-5 Ie, 10°5 11°8 
SO &4 42 18°3 13 9:5 9 
70 70 35 13 10 5) 6:5 
55 58 32 13 10 68 
45 45 25 10°5 5d 
40 38 21:5 9 5) ae ¥ 
25 24°5 12 65 2 1:7 1:8 
12 10°5 6°5 
Distribution. East side of Atlantic from the Azores to Iceland; 
Bermuda; North Sea; Mediterranean. 5-530 fms, 
