REPORT ON THE ASTEROIDEA, 381 
Disk large, convex, and much inflated. Rays elongate, narrow, and more or less 
rounded cylindrically. Margin rather angular, the marginal plates being very incon- 
spicuous. Interbrachial ares wide and rounded. Actinal surface concave and deeply 
depressed within the disk (possibly this is either a mere body contraction, or may 
indicate the formation of a nursing cavity such as occurs in some forms of Asterias and 
Echinaster). The actinal surface of the rays is slightly convex. 
The abactinal area is covered with small irregularly disposed plates, which bear 
groups of from three to ten spinelets. The spinelets are short, subequal, papilliform, 
covered with membrane and imbedded at the base in a thick fleshy mass, the groups 
looking more like irregular echinulated masses than paxille. The form of the masses 
varies considerably, and elongate groups are not infrequent. Large and smaller groups 
are interspersed irrecularly, and all are widely spaced. In the interspaces are numerous 
large papulee, and groups of three to five may be counted. 
The marginal plates, which are very small and quite inconspicuous, are at first sight 
scarcely distinguishable from the actinal and abactinal plates on the median part of the 
ray, and much irreeularity occurs in their size. In the interbrachial arc and on the 
outer half of the ray they are more distinct; and the superior and inferior series are 
seen to alternate to a certain degree. The plates, which are subequal and similar in 
character, are covered with small papilliform granules, skin-covered and imbedded in 
membrane similar to those on the abactinal and actinal plates. More than fifty infero- 
marginal plates may be counted between the median interradial line and the extremity, 
but it is scarcely possible without dissection and preparation to count. the number 
accurately on account of their small size and the interference of intermediate plates on 
the middle part of the ray. 
The adambulacral plates are short, and their armature consists of :—(1.) A single large 
spine on the furrow margin, which is very robust and cylindrical at the base, but flattened 
and truncate at the tip like a chisel in the direction transverse to the axis of the ray. 
These spines are thickly covered with membrane. On the ten or twelve plates near the 
mouth there are two spines on the furrow margin, very obliquely placed, the adoral one of 
the pair being pushed far back. (2.) On the actinal surface of the plates is a lineal series 
of three short, subequal, skin-covered, papilliform spinelets, much smaller than the furrow 
series, slightly tapering at the end but obtuse, the direction of the series being usually in a 
straight line behind the furrow spine, at right angles to the furrow, but sometimes slightly 
oblique. Occasionally there is a fourth spine in this series, and sometimes the line of the 
series is slightly curved. 
The actinal intermediate plates are small and form well-defined longitudinal series, 
two of which extend nearly to the end of the ray: about eight series may be counted on 
each side of the median interradial line. Each plate bears a group of from three to seven 
short, subequal, slightly tapering spinelets, covered with skin and imbedded at the base 
