45 
The Echinodermata of jNeiv Trunswic}.. 
nearly related to Oribrdla mnguinohnta, which, except for the difference 
in the number of the rays, it closely resembles. 
It has been found even in our own waters as large as twelve 
inches in diameter, but most specimens would not much exceed half 
that size. It may have from seven to eleven ra3^s, ten being perhaps the 
most common number. Each ray is nearly round in section, tapers 
evenly from base to tip, and is about as long as, or a little longer than 
the diameter of the disk. The ambulacral furrows, containing each two 
rows of tube-feet, are narrow and can be completely closed in b}' the 
bringing together of the edges of the furrow. The madreporic body 
lies about half way between the centre of the disk and an angle of the 
rays. The spinulation is notunlike that of Crihrella and differs consid- 
erably from that of Crossaster, in comparison with which it has quite a 
smooth appearance. The upper surface of both disk and rays is nearly 
covered with short blunt tubercles, each of which bear a crown of from 
five to ten short, rough, blunt spines, so small as to need a lens to prop- 
erly distinguish them. These are scattered irregularly over the disk, 
but on the arms run in rather regular rows obliquely from the margin 
to the median line. On the under side are conspicuous rows of two 
kinds of spine-clusters, both of which kinds are flattened in a plane at 
right angles to the length of the ray. One of the rows, in which the 
clusters are made up of many slender, short spines united together at 
their bases, occupies all the outer margin of each ray, and curving 
evenly around the angle between any two contiguous ones shows no 
breaks between the marginal rows of the arms. This row therefore 
forms a band around the entire margin of the under side, with the ex- 
ception of a minute break at the tip of each ray. A row of much 
smaller clusters follows this on its outer side throughout its course, but is 
upon the sides of the rays rather than on their under surfaces. The 
other conspicuous rows are those which start near the mouth and run 
along each side of each ambulacral furrow to Ihe tips of the rays. The 
clusters are made up of much longer and stouter spines than the for- 
mer row, some six or seven in number, united at their bases and 
placed all in one plane, which is as already stated at right angles to the 
length of the ray. Another row, consisting of a line of single spines, 
may be seen quite within the ambulacral furrow. The remainder 
of the under surface contains clusters of larger spines than those of the 
upper surface. The mouth plates are large and strong and bear several 
stout spines, which form powerful mouth-papillae. 
In color it varies much, though not to such a degree as Crossaster or 
Crib)*ella. Abov^it is usually some shade of purple or red. and below of 
a straw or cream color, and the color varies with the sex. In our waters 
the upper side is nearly always purplish red and the under light orange. 
It lives upon rocky or other hard bottoms in clear water, and in its 
