152 RECENT UNSTALKED CRINOIDS 
comparatively small and compact; the ventral surface takes 
the form of a high rounded dome reaching to the height 
of the base of the ninth brachial; from the central (highest) 
point of this dome the ambulacra, which reach the arms 
at about the ninth brachial, are supported upon high 
narrow bridges as in Gephyrocrinus, Thalassocrinus and 
Ptilocrinus; up to the height of the general surface of the 
disk the pinnules are connected with it by webs or thin 
sheets of perisome, resembling the thicker sheets which 
support the brachial ambulacra in their passage to the 
arms; a strip of thickened perisome extends interradially 
to the union of the radials, just above which it bears a 
cluster of about a dozen small disconnected rounded cal- 
careous plates. 
The syzygial faces in this species show five radial ridges 
only, one in the dorsoventral line and two on either side 
of it; the ridges are very high so that the ligament fibers 
are long, appearing in dorsal view almost or quite as long 
as those of the neighboring dorsal ligaments. 
Type locality. — »Siboga” Station N°. 177. 
Atelecrinus sulcatus, sp. nov. 
This species differs from A. wyvillei in its more sharply 
conical centrodorsal which has a pentagonal base and bears 
interradial ridges proximally which become marked inter- 
radial furrows between the columns of cirrus-sockets, and 
in the greater height of the lateral ridges bordering the 
cirrus-sockets. 
The centrodorsal is sharply conical, 3 mm. broad at the 
base and 4 mm. in vertical height; the cirrus-sockets are 
arranged in ten columns, four, more rarely five, to a column; 
the columns of each radial area are close together, those 
of adjacent radial areas being separated by shallow furrows 
which basally are in width nearly equal to the diameter 
of the adjacent cirrus-sockets, but become gradually nar- 
rower distally; the interradial separation of the cirrus- 
Notes from the Leyden Museum, Vol. XXXIV. 
