OF TIE SIBOGA-EXPEDITION. 13) 
sockets is always somewhat greater than the midradial 
separation; each cirrus-socket is bordered proximally and 
laterally by a horse-shoe shaped rim which proximally 
scarcely rises above the general surface of the centrodorsal 
but on either side stands out as a high ridge so that in 
lateral view the sides of the centrodorsal appear strongly 
serrate, the longer side of the teeth being gently convex, 
roughly parallel with the dorsoventral axis, the shorter 
slightly concave, at right angles to this axis; these lateral 
ridges are thickened gradually distally, but terminate rather 
abruptly just after attaining their maximum height and 
thickness so that the border of the cirrus-sockets distal to 
them is even with the general surface of the centrodorsal ; 
the basal outline of the centrodorsal is pentagonal, each 
side being slightly and evenly concave; five well marked 
rounded interradial ridges are present which slowly decrease 
in height and disappear at about the distal border of the 
first cirrus-socket; these ridges mark the angles of the 
pentagon when the centrodorsal is viewed basally. 
The basals form a very narrow band of almost uniform 
height between the radials and the centrodorsal; they are 
slightly higher in the angles of the calyx than elsewhere, 
their dorsal surface being here raised to form a proximal 
continuation of the interradial ridges on the centrodorsal. 
The radials and the post-radial structures do not differ 
essentially from those of A. wyvillei. 
The first pinnule is on the sixteenth brachial. 
Type locality. — »Siboga” Station N°, 85. 
Atelecrinus anomalus, sp. nov. 
The centrodorsal is very long, cylindrical in the basal 
third, conical in the distal two thirds, rounded at the tip, 
1.8 mm. in basal diameter and about 3 mm. long; the 
cirrus-sockets are confined to the distal conical portion; 
they are arranged in ten evenly spaced columns, three 
(rarely two or four) to a column; the surface of the centro- 
Notes from the Leyden Museum, Vol. XXXIV. 
