ei y 
924 TRANS. OF THE ACAD. OF SCIENCE. 
and bear a small, prominent, primary tubercle, mince: is pe 
ly perforated, and situated on an elevated, smoot 
the border of which it is separated by a dee ep, arsine pec 
Around the base of this boss is a broad, circular areola, the 
very obscure, radiating ruge. The areola is pe by a 
ting of closely-set nooondary tubercles, arranged in a single 
line. Exterior to this ring the surface is thickly oulded on 
the ambulacral side with fine granule and secondary 
cles. The primary spines are elongate-fusiform, very variable 
in length and rather strongly curved at their bases. Some 
Specimens are also slightly curved near the apex, the eurva- 
ture being in an opposite Siepotibes to that of the base. "The 
transverse section in most specimens is multangular, bu 
sometimes it appears to be nearly ee The ring . the 
base is small, finely milled on the edge, and set 0 
axis of the spine. The surface is very inl waiaied lo 
dinally and thickly studded with s rt spines, idence! « 
are dir d obliquely upwards. They avs 
angles: principal spines in from eight to twelve og 
~ Dime the rimary spines vary from 
bo arg ngth, and a i Brektaet “diameter from ro to ol 
fro 
| - The edges are > garish e re ees 
