ANNOTATED LIST. 155 
HOLOTHURIOIDEA. SEA-CUCUMBERS. BECHE-DE-MER. 
Holothurians form not only a conspicuous but a most important part of the 
Torres Strait marine fauna, for many of the species are collected, cooked, and dried 
for export to China under the French name béche-de-mer or the Malay term tre- 
pang. Thus prepared they are most uninviting-looking objects, but they are 
regarded by the Chinese as a very desirable article of diet. Alive and exhibiting 
their natural colors and form, many holothurians are really beautiful objects, but 
it must be granted that the majority are unattractive and often repulsive. Elon- 
gated, sometimes worm-like, they show no external obvious resemblance to the 
other classes of echinoderms, and no one unfamiliar with their anatomy would 
think of the really close relationship. The identification of the numerous species 
is not easy, as it must be based finally on the calcareous particles of the skin, and 
many of the obvious external characters are so subject to growth-changes and indi- 
vidual diversity that a large proportion of the specimens taken are perplexing 
even to one familiar with the group. Added to this is the fact that specimens 
must be preserved in fluid (commonly alcohol) and in the preserved condition size, 
color, and proportions are altered, often to such a degree that one can hardly believe 
the changes possible. We are still so ignorant of growth-changes and of the limits 
of individual diversity, even in the best-known species, that many forms now 
recognized by name may prove merely nominal, while in other cases it seems prob- 
able that two or more species are now concealed under a single name. As a result 
of these difficulties, many identifications of holothurians are open to serious doubt, 
and this is particularly true of the East Indian and Australian species. Hence 
one can not feel confidence in the records from many localities, and the actual 
distribution of very few species is known with any degree of reliability. 
The Challenger took only 4 species of holothurians in the Torres Strait region, 
and as these were identified by Théel, perhaps the best systematist who has special- 
ized on holothurians, one feels very sure of the species. According to Bell, the 
Alert brought home 9 species of holothurians from the region, none of which was 
taken by the Challenger. But his supposedly new Actinocucumis difficilis is prob- 
ably identical with A. typica, which was collected by the Challenger. Semon gath- 
ered 10 species during his stay at Thursday Island, none of which was found by 
the earlier collectors. I was more fortunate than my predecessors, for during our 
stay I secured 52 species, of which only 7 had been previously taken, 3 by the 
Alert and 4 by Semon. There are thus 68 species included in the present report, 
but unfortunately very few of them are sufficiently well known to make them of 
much service in the discussion of questions of distribution. 
Holothurians are found in a great variety of situations, but, excepting the 
largest species, which lie quietly or move about sluggishly on sandy or grassy bot- 
toms, they seek shelter either through burial in sand or sandy mud, or by crowding 
themselves into the crannies and cavities of coral-rock fragments or of the dead 
portions of coral colonies. Occasionally they live on the under side of rock frag- 
ments or on the sand beneath such rocks. While not truly gregarious, some species 
are often represented by 4 or 5 individuals under one shelter, and species which 
