INTRODUTION. vil 



all those known, of which three, all unstalked, are new. Two of these new genera are closely 

 related to others previously described, but the third is an extraordinary and unique t\ 



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 : 



Thysanometrinae A piocrinidae 



Isometrinae Phrynocrinidae 



Heliometrinae Plicatocrinidae 



Holopodidae 



the first 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 extreme 

 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 {Proisocrinus ruberrimus) west of Luzon. The family, though so important as 

 a fossil, is not otherwise known from the recent seas. 



The "Challenger" secured a specimen of a species of Plicatocrinidae (recorcled as 

 "}Hyocrinus bethel lianits") in 5°3i'N. J 145° 13' E., at a depth of 4185 Metres; the "Albatross" 

 secured another {Thalassocrinus pontifer) in the Moluccas. 



The Phrynocrinidae remain known only from southern Japan and the Hawaiian Islands, 

 one genus (Phrynocrinus and Naumachocrimis respectively) from each locality; there are in 

 existence three specimens altogether, two of one and one of the other, all three incomplete. 



The genera Democrinus, Bythocrimis and Monachocrinus of the Bourgueticrinidae were 

 first found in the East Indian region by the "Siboga"; but it is quite possible that the " Rhyzo- 

 crimts" mentioned by Korotxeff *) is Democrinus weberi. 



For the sake of comparison it may be mentioned that the "Albatross" also failed to 

 secure representatives of 7 families and subfamilies : 



Heliometrinae Holopodidae 



Isometrinae Bourgueticrinidae 



Perometrinae Phrynocrinidae 

 Tropiometridae 



1) Buil de 1'Acad. roy de Belgique, sér. 3, vol. 12, 1886, p. 558. 



