256 
BULLETIN OE THE UNITED STATES FISH COMMISSION. 
HOLOTHURIOIDEA. 
HOLOTHU RIANS, SEA-CUCUMBERS, SEA-SQUIRTS, ETC. 
The holothurians of the West Indies are not nearly so well known as the sea- 
urchins, so that every new collection is likely to contain undescribed species, or at 
least to extend the range of those previously known. About 35 species have been 
described from the West Indian region, or are known to occur there, and of these less 
than half a dozen are exclusively deep-water forms. It appears, therefore, that the 
great majority of the holothurians of this region are littoral forms, and many of them 
are apparently quite limited in their range. But as yet we know too little of their 
natural history, or of what constitute good specific characters in the group, to draw 
any important conclusions. Species have been made on form, color, size, number of 
tentacles, and other inconstant characters to such an extent that the whole subject 
of West Indian holothurians needs a thorough overhauling, especially since they 
constitute one of the most characteristic groups of the shallow-water fauna. 
The Fish TIawk collection contains 85 specimens of sea-cucumbers, representing 
10 species, all but one of which are littoral forms. Curiously enough, all these littoral 
forms belong to the single family Aspidocliiroim , so that probably only a small part 
of the holothurian fauna of Porto Rico appears in the collection. 
The following artificial key will help to distinguish adult specimens of the above 
given species, and also includes one other species collected by Mr. Gray. It is hard 
to give distinguishing characters among holothurians, except by means of the micro- 
scopic calcareous particles in the skin. As far as possible the characters used below 
can be easily seen without the aid of a microscope; but it must be remembered that 
the number and arrangement of the tentacles, pedicels, and papilke are often very 
different in the young from what they are in the adult. They are usually fewer in 
number and show a more orderly and definite arrangement. 
A. Tentacles long, slender, unbranehed. Body-wall firm and spiny. Color white. Deep-sea form. 
Ecldnotnicuinis asperrima, (1) 
B. Tentacles (normally 20) comparatively short, with numerous branches, crowded into a fiat disk at 
the end. Body-covering soft. Shallow-water forms. 
I. Size large, up to a foot or more in length. Found on sandy or muddy bottom. 
a. Brown or black above; yellowish, reddish, or almost white below, and more or less on sides. 
Body-wall tough and leathery. Pedicels numerous on ventral side, not arranged in 
rows Holothuria mexicana. (8) 
b. Color extremely variable; the extremes are uniform blackish-brown, without markings, and 
uniform light buff with a few small spots of dark brown. Between these two extremes 
all possible combinations of light and dark occur, but the commonest form is buff, con- 
siderably blotched with large patches of dark brown. Body-wall, though thick, soft and 
slimy. Pedicels numerous, arranged distinctly in three broad longitudinal rows on 
ventral surface. Stichopux iiiobii. (2) 
II. Sizesmall, rarely 8 inches long. Usually found amongrocks, often buried in sand under loose slabs. 
a. Body covered with more or less wart-like conical papillae. Pedicels few, irregularly scattered, 
or none Holothuria impatiens. (7) 
b. Pedicels arranged in 3 longitudinal series on ventral surface. Cuvier’s organs very notice- 
able, pure white in living animal Holothuria captiva. (3) 
c. Pedicels thickly crowded ventrally, less numerous dorsally; few papill®, if any Holothuria glaberrima. (5) 
d. Body very thickly covered with pedicels ventrally and with papillse and pedicels dorsally. 
Holothuria densipedes. (4) 
e. Body elongated, with scattered and rather few papillre on dorsal surface, and irregularly 
scattered pedicels on ventral. 
1. Blackish and whitish or light gray, mottled with darker; sometimes more or less tinged 
with yellow Holothuria grisea. (6) 
2. Grayish, but more or less decidedly yellow, with fine purple markings and blotches of the 
same color Holotlnmamthbuni. (9) 
3. Brownish or purplish, more or less indistinctly marked with darker blotches. . Holothuria surinammsix. (10) 
C- Tentacles 15, pinnate. Body long and slender, without pedicels . .Synapta lappa. (11) 
