^i.kD'E.^—Echinodermata from the 8.W. Coast of Ireland. 695 
The siipradorsal membrane is rather thin and very fibrous, the fibres 
in the tissue being very fine, numerous, and closely interlacing. The 
paxillae are numerous and closely placed, having crowns of three or 
four (or more) long, thin, needle-like spinelets, articulated on a long 
pedicle. In the central region of the disk more spinelets may be 
present. The spinelets have the appearance of being very protuberant, 
the membrane hanging closely for a considerable distance from the tip, 
which gives a very spinose character to the abactinal surface. No 
regularity in the arrangem.ent of the paxillse is superficially discernible. 
The membrane is semi-transparent, except when old and thick. The 
spiracula are small, irregular in position, and few in number. The 
oscular orifice, though moderately large, is inconspicuous ; the spinelets 
of the valves are numerous, long, and much crowded. 
The ambulacral furrows are broad, slightly petaloid, and taper 
towards the extremity. The tube-feet are very large, with a large, 
puffy, centrally-invaginated terminal disk. The armature of the 
adambulacral plates consists of a comb of five spinelets. The inner- 
most spine is the smallest, measuring from 1*75 to 2 mm. in length, 
and is placed at the aboral end of the plate, and the outermost spine is 
the longest, being between 5 and 6 mm. long. The comb forms a 
regular semicircular curve, passing from the aboral end of the furrow 
margin of the plate to the outer margin of its actinal surface, the 
comb, which traverses the actinal surface of the plate, being curved 
round ■ aborally at the margin of the furrow. All the spinelets are 
united by web, which is delicate, semi-transparent, and deeply indented 
between the spinelets ; and it falls almost perpendicularly from the 
outermost spine of the comb, and does not extend far out upon the 
actino -lateral spines. 
The segmental apertures are moderately large. The aperture- 
papilla is thick and rather jawbone-shaped, and is free on the aboral 
side only, forming a slightly angulated lip. 
The mouth-plates are of moderate size, and, though rather short, 
are widely expanded laterally. The keel along the median line of 
junction is high and broad, and prominent aborally. Each plate bears 
an armature of five mouth- spines, which form a webbed comb situated 
entirely on the horizontal margin of the plates ; the innermost spine is 
the longest, measuring between 5 and 6 mm. in length, the outermost 
I two very small, the last being about I'S mm. in length. The series of 
spines on each plate are united by web, but the two combs of a mouth 
angle are separate and independent. No secondary or superficial spines 
are present on the actinal surface of the plates. 
E.I. A. PEOC, SEE. III., VOL. I. 3D 
