150 RECENT UNSTALKED CRINOIDS 
the lateral angles extend considerably beyond the distal 
angles of the IBr,; the distal edges are everted and very 
finely spinous. 
The ten arms are 30 mm. long and resemble those of 
other species of the genus; the distal edges of the brachials 
are moderately everted and finely spinous. 
P, is about 6.5 mm. long with more than fifteen seg- 
ments of which the first two are broader than long, the 
third is about as long as broad, the fourth is half again 
as long as broad, and the following become excessively 
elongated with swollen projecting and overlapping spinous 
distal ends; P, is 4 mm. long with eleven or twelve seg- 
ments, stouter than P, but exceedingly slender distally, 
the segments beyond the third being excessively elongated ; 
there is a large gonad on the fourth-seventh segments. 
Type locality. — »Siboga” Station N° 52. 
Family ATELECRINIDAE. 
Atopocrinus, gen. nov. 
Genotype. — Atopocrinus sibogae, sp. nov. 
Diagnosis. — Centrodorsal sharply conical, longer than 
broad at the base; the surface is divided into five radial 
areas by five strong interradial ridges, and each radial area 
is bisected by a similar ridge; the cirrus-sockets are there- 
fore arranged in ten columns. 
The lower portion of each cirrus-socket projects outward 
forming a roof over the cirrus-socket next below; each 
cirrus-socket bears two lateral ridges which extend some- 
what beyond the crests of the interradial and radial ridges 
so that these appear strongly serrate. 
The five basals are extremely reduced so that they appear 
externally as five narrow lines separating the basal rays 
from the centrodorsal; the basal rays are large and well 
developed. 
There are five arms, no [Br series being present; the 
Notes from the Leyden Museum, Vol. XXXIV. 
