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this fact I reexamined the whole sample of bottom material and 
succeded in finding, besides a good number of disks, a nearly corre- 
sponding number of specimens of an Ophiurid without disk. Though 
not a single specimen was found with the disk preserved it could not 
be doubted that the loose disks really belonged to this Ophiurid; other- 
wise there would be no disks corresponding to the arms and no 
arms corresponding to the disks. Also another species was found, 
a species of the genus Ophiacantha (or at least nearly related to 
that genus), which had thrown its disk off, but of this also intact 
specimens were found, so that there was no possibility of a mistake. 
It was thus, so to speak, along the statistical way that the loose 
disks and arms were proved to belong together. 
Though it is certainly a well known fact that some Ophiurids 
have the custom of throwing off their disk through autotomy when 
hurt in some way, the present case has seemed to me of a some- 
what extraordinary ,interest and well worth to be described in detail, 
the more so as the Ophiurid represents a new genus. I shall 
describe it here under the name of 
Microphiura decipiens n.g., n. sp. 
Diameter of the disk 2 mm., length of arms ca. 10 mm., width 
of arm at the base 0.2—0.3 mm. 
There is only one mouth-papilla on each side of the mouth- 
angles, occupying the whole side; at the apex a single small, tri- 
angular papilla is found (Pl. II. Fig 1), and below this there is 
one single tooth. The plates following outside the mouth-papilla, 
representing the first adambulacral plates, are very distinct, straight, 
of the same width in their whole length, from the median line, 
where they join, to their outer end, which joins the first ventral 
plate and the inner tentacle pore. The side-mouthshields are some- 
what broader, otherwise mainly of the same shape, only their outer 
edge being slightly curved. The mouth-shields are small, triangular, 
occupying a somewhat unusual position, being placed nearly verti- 
cally, slightly curving round the edge, so that they are slightly 
