696 
Proceedings of the Royal Irish Academy. 
The first or most adoral transverse comb of the adambulacral plates 
of two neighbouring rays are closely approximated at their attachment 
to the actinal membrane behind the aboral peak of the month-plates, 
but they are not joined together. 
The actino -lateral spines are long, rather delicate, and closely placed, 
and extend to the margin of the actinal surface. The spines are 
horizontal in their disposition, forming a flat actinal surface to the disk ; 
and the fringe appears to extend very slightly beyond the margin. The 
longest spine, which measures 11 mm. or a little more, is the seventh 
or eighth, counting from the mouth -plates ; and those on the outer part 
of the ray are very small. 
Colour in alcohol, a dirty ashy grey, with a slightly purplish tinge 
on the actinal surface. 
Locality.— 'Lai. 51° 1' IS"., Long. 1 P 50' W. Depth 750 fathoms. 
Remarhs. — This species presents in a very striking manner the 
f acies of a Hymenaster^ and appears in many respects to hold an inter- 
mediate position between that genus and Pteraster. It may readily be 
distinguished from other forms by the disposition of the actino -lateral 
spines, by the character of the armature of the adambulacral plates, and 
by the absence of secondary or superficial spines on the actinal surface 
of the mouth-plates. 
14. Hymenaster giganteus^ n. sp. (Plate XXYIII., figs. 1-3.) 
Marginal contour pentagonal, the indentation of the interbrachial 
arcs being slight, and more or less masked by an irregular and excres- 
cent growth of the web. Rays slightly produced and recurved. The 
minor radius is in the proportion of from 64 to 68 per cent. E = 160 
mm., r = 102 mm. These measurements are, however, only approxi- 
mate, and are taken on the actinal surface, where there is much 
distortion and inflation. The general form of the example described is 
more or less distorted by inflation. On the abactinal surface the 
radial areas are well marked out, distinct from the fringe and inter- 
radial membrane, and have the appearance of being elevated above the 
general surface as viewed from above superficially. The lateral web 
is largely developed, thick, full, and in consequence somewhat irregu- 
lar. 
The supradorsal membrane, which is thick and opaque, is furnished 
with very numerous clearly-defined muscular fibres, which radiate from 
the tips of the spinelets and pass to those standing in close proximity 
around, the bands crossing at various angles, overlying and underlying 
one another, and forming a thick interlacing and irregularly reticulated 
