Microphiura decipiens n. g. n. sp. 
A remarkable new West Indian Ophiurid. 
By 
Dr. Th . Mortensen . 
(With Plate II). 
Wken examining some bottom material from ca. 500 fathoms 
from off Frederiksted, St. Cruz, Danish West Indies, brought home 
by me from a journey to the West Indies in 1905 — 6, Dr. H. J. 
Hansen called my attention to some small organisms which he 
had noticed in the material, and which he thought might possibly 
be Echinoderms. I was at first very puzzled by these organisms. 
That they were Echinoderms could not be doubted, but of which 
class was not easily decided. They were of a peculiar cup-shape 
(PI. II. Figs. 2—4), with a rather regular plating and a five-rayed 
opening on the flat side; the diameter was ca. 2 mm., the height 
ca. 0.5 mm. It seemed as if they must be complete specimens, 
it being impossible to detect any traces of their having been torn 
or cast off by any animal. The first suggestion, that they were 
cast-off disks of an Ophiurid, seemed then unacceptable. In faet, 
they reminded one most of the long extinet Edrioasteroids, one 
main character, however, being decidedly against the suggestion of 
their relation to that most interesting class, viz. the lacking of an 
anal opening. The question of their affinities evidently had to be 
solved through the study of their anatomy. Having had sections 
made through a pair of decalcified specimens I could no longer 
remain in doubt about the systematic position of the problematical 
organisms. It was evident that they were really, as at first 
imagined, the thrown off disks of an Ophiurid. Having established 
14* 
