58G THE VOYAGE OF H.M.S. CHALLENGER. 



21. Asterias (Stolasterias) stichantha, n. sp. (PI. CVI. figs. 1-4). 



Kays five. E = 158 mm. ; r = 17 mm. ^ E > 9 r. Breadth of a ray at the base, 

 about 18 mm. 



Eays elongate, broad and robust at the base, tapering gradually to a pointed extremity. 

 Abactinal surface of the rays roundly convex and having a subcylindrical appearance 

 when viewed from above. Disk small, slightly convex, but not higher than the rays. 

 Interbrachial arcs acute. 



The skeletal plates of the rays are disposed with great regularity, and those of the abac- 

 tinal surface bear single uniform spinelets. Nine regular longitudinal series of equally 

 spaced, isolated spinelets may be counted on the abactinal surface of the rays, the 

 spinelets of the outermost series on each side being a shade larger than the others, and 

 represent in my opinion a supero-marginal series. The median radial series is not different 

 from the others. The spinelets, which are cylindrical, tapering, and pointed, measure 

 from 2*5 to 3 - 5 mm. in length, and are surrounded at the base by one or two circlets of 

 rather large, flattened, peculiarly blunt, skin-covered forcipiform pedicellariae, which have 

 to a certain extent the appearance of being appressed to a slightly convex elevation sur- 

 rounding the base of the spine. Between adjacent wreaths is a space of naked membraue, 

 and large isolated forficiform pedicellariae with strong and coarsely denticulate interlocking 

 extremities are present here and there. The papulae are in small, compact, isolated groups, 

 with seldom more than five or six in each, except upon the disk, where the number is 

 rather greater. The infero-marginal plates bear two spinelets, which stand as an obliquely 

 placed pair ; these spinelets are a little longer than the supero-marginal series, very robust 

 at the base and thickly skin-covered, and each bears on its outer side a small tuft of pedi- 

 cellariae similar to those above described. The small but distinct space of naked mem- 

 brane between the supero-marginal and infero-marginal spines is occupied only by small 

 isolated groups of papula? and an occasional large forficiform pedicellaria. Between the 

 infero-marginal plates and the adambulacral plates is a single series of large isolated 

 papulae, one standing between each pair of infero-marginal spines and near the base of the 

 innermost spine of the pair. 



The adambulacral plates are very small, and their armature consists of two rather loug, 

 equal, cylindrical, and slightly tapering spinelets which radiate slightly apart. At the 

 base of the ray they measure from 3 '5 to 4 mm. in length. Along the margin of the 

 furrow, at the base of the innermost spines, are a number of large, elongate, pointed-jawed, 

 forficiform pedicellariae with long peduncles. There may be one to each alternate plate, 

 but sometimes they occur more frequently. 



The ambulacral furrows are very wide, and the tube-feet, which have small, fleshy, 

 centrally invaginated terminal disks, are quadriserial in their arrangement throughout. 



The mad repori form body, which is rather large and circular in outline, is situated 

 about midway between the centre of the disk and the margin ; its surface is marked 



