770 
Proceedings of the Royal Society 
1. R. lofotensis, M. Sars. 
This species was discovered in the year 1864, at a depth of about 
300 fathoms, off the Loffoden Islands, by Gr. 0. Sars, a son of 
the celebrated Professor of Natural History in the Uuiversity 
of Christiania; and it was described in detail by the latter in the 
year 1868. It is evidently a form of the Apiocrinidae still more 
degraded than Bourguetticrinus , which it closely resembles. The 
stem is long and of considerable thickness in proportion to the 
size of the head. The joints of the stem are individually long 
and dice-box shaped, and between the joints spaces are left on 
either side of the stem alternately, as in Bourguetticrinus , and in 
the pentacrinoid of Antedon for the insertion of fascicles of con¬ 
tractile fibres. Towards the base of the stem branches spring from 
the upper part of the joints; and these, each composed of a suc¬ 
cession of gradually diminishing joints, divide and re-divide into a 
bunch of fibres which expand at the ends into thin calcareous 
laminae, clinging to small pieces of shell, grains of sand—anything 
which may improve the anchorage of the crinoid in the soft mud 
which is nearly universal at great depths. 
In Rliizocrinus the basal series of plates of the cup are not dis¬ 
tinguishable. They are masked in a closed ring at the top of the 
stem, and whether the ring be composed of the fused basals alone, 
or of an upper stem-joint with the basals within it forming a 
“ rosette ” as in the calyx of Antedon , is a question which can 
only be solved by a careful tracing of successive stages of develop¬ 
ment. The first radials are likewise fused, and form the upper wider 
portion of the funnel-shaped calyx The first radials are deeply 
excavated above for the insertion of the muscles and ligaments 
which unite them to the second radials by a true (or moveable) 
joint. One of the most remarkable points in connection with this 
species is, that the first radials, the first joints of the arm, are 
variable in number, some examples having four rays, some five, some 
six, and a very small number seven in the following proportions. 
Out of seventy-five specimens ex am fried by Sars, there were— 
15 
with 
4 arms. 
43 
5 ? 
5 „ 
15 
V 
6 „ 
2 
>) 
7 „ 
