116 Mr. A. H. Clark on a 
transverse ridges may be counted, which are from 0°6 mm. 
to 0°8 mm. apart. Hach of the plates in the transverse rows 
bears from four to seven spines, usually in a somewhat 
irregular single median linear series; occasionally one of 
the spines may be more or less enlarged. Among these 
spines are many minute pedicellariz. 
Except where it is supported by plates the abactinal 
membrane, which is very thin, is collapsed upon the ambu- 
lacral ridge, which is plainly visible through it. 
Beyond the genital region the transverse bands of plates 
become more widely spaced, separated from each other by a 
band of naked skin, the spines at the same time becoming 
reduced to a narrow band of pedicellarie. There is a narrow 
transverse band of plates over the lines of union between 
all the ambulacral ossicles, and another over their central 
portion. These bands become narrower and the plates 
composing them more delicate, but they persist to the end 
of the arms. 
The adambulacral plates at first are broader than long, 
becoming longer than broad after the proximal half of the 
genital region, and very narrow and elongate distally. On 
the furrow-margin they bear two very delicate spines, one 
at either end of the plate, which reach halfway across the 
furrow and are covered with a delicate membrane bearing 
one or two pedicellariz. On the aboral end of the plate 
above, and somewhat proximal to, the distal furrow-spine 
there is a much longer and stouter spine, twice as long as 
the furrow-spines and correspondingly stout, sheathed in 
membrane and bearing numerous pedicellarie. Beyond 
this and slightly proximal to it, situated approximately on 
the actinolateral border of the plate, there is a long stout 
spine nearly double the length of the preceding, enshrouded 
in thick membrane covered with very numerous pedicellarie ; 
as far as the end of the adoral fourth of the genital region 
the end of this spine is expanded into a club-like, bifurcate, 
or bluntly three- or four-pointed tip, but beyond this point 
the tip is slender and sharp. On the abactinal border, 
mounted on a small truncated conical plate affixed to the 
adambulacrals, there is a long slender sharp spine, longer 
than the preceding, sheathed in thin membrane. 
The mouth-spines are two, thickly beset with pedicellaria. 
The colour in alcohol is brownish yellow. 
Type. Cat. no. 36950, U.S.N.M., from ‘ Albatross ’ 
Station 2807, Galapagos Islands, in 812 fathoms. 
