INTRODUTION. VII 
all those known, of which three, all unstalked, are new. Two of these new genera are closely 
related to others previously described, but the tiiird is an extraordinary and unique type. 
The 71 genera are included in 21 families and subfamilies (19 comatulid and 2 stalked), 
all previously known. 
It is often quite as interesting and instructive; to consider what is lacking in a collection 
as what is present. The 7 families and subfamilies of which the "Siboga" did not secure 
representatives are : 
Thysanomelrinae Apiocrinidae 
Isometrinae Phrynocrinidae 
Heliometrinae Plicatocrinidae 
Holopodidae 
the tirst three comatulids, the last four stalked types. 
Thus we still know the Holopodidae only from the Caribbean Sea, and the Isometrinae 
only from the Antarctic regions. A representative of the Thysanometrinae is known to occur 
in the region traversed by the ".Siboga", where it was collected both by the "Challenger" and 
by the "Albatross"; its absence from the "Siboga" collection emphasizes anew the e.xtreme 
difficulty of securing a complete collection of the crinoids inhabiting any one locality. 
The Heliometrinae are represented by a single genus in the Indo-Pacific region which has 
only been reported from southwestern Japan and the Arabian Sea, a single species represented 
by a single specimen from each locality. 
The "Challenger" dredged a .single very fragmentary specimen of a species of Apio- 
crinidae {Carpenterocrinus mollis) south of Japan, and the "Albatross" a single specimen of 
another genus [Proisocriiius ruberriinics) west of Luzon. The family, though so important as 
a fossil, is not otherwi.se known from the recent seas. 
The "Challenger" secured a specimen of a species of Plicatocrinidae (recorded as 
'"^ Hyoirinus bethel lianus') in 5°3i'N., 145° 13' E., at a depth of 4185 Metres; the "Albatross" 
secured another [Thalassocrimts pontifer) in the Moluccas. 
The Phrynocrinidae remain known only from southern Japan and the Hawaiian Islands, 
one genus {Phrynocrinus and Naiiiiiachocrimis respectively) from each locality; there are in 
existence three specimens altogether, two of one and one of the other, all three incomplete. 
The genera Democrimts, Bytliocriniis and Jfottachocrmus of the Bourgueticrinidae were 
hrst found in the East Indian region by the "Siboga"; but it is quite possible that the '^ Rhyzo- 
ci'inus" mentioned by Korotnkff ') is Deinoci'inus zveberi. 
For the sake of comparison it may be mentioned that the "Albatross" also failed Xo 
secure representatives of 7 families and subfamilies : 
Heliometrinae Holopodidae 
Isometrinae Bourgueticrinidae 
Perometrinae Phrynocrinidae 
Tropiometridae 
l) Bull dc I'Acad. roy de Belgique, ser. 3, vol. 12, 1886, p. 55S. 
