178 THE ECHINODERMS OF TORRES STRAIT. 
from 0.050 to 0.100 mm., while the width is about half as much. Supporting rods of 
pedicels (pl. 38, fig. 20) not very abundant, but large, flat, branched, and perforated at 
the ends; terminal plates present. Supporting rods of tentacles not very abundant, 
nearly straight, rough or spiny at tips. Color in life white, with or without a brown tinge 
and two series of dark blotches on dorsal surface; sometimes with numerous small 
blackish spots; in aleohol the white becomes yellowish or brownish; tentacles pale yellowish 
or brownish; pedicels tipped with yellow. Surface of body commonly more or less covered 
with sand-grains, concealing the true color; these are apparently held by a cement-like 
mucus which does not release them readily even after death. 
Holotype: M. C. Z. No. 1029; from under a rock-fragment, on southeastern reef- 
flat, Mer, Murray Islands, Torres Strait. 
This holothurian is fairly common at Mer, and I also took a specimen at Green Island, 
Queensland, and at Hilo, Hawaii. A specimen from Port Galera, Mindoro, Philippine 
Islands, is in the Museum of Comparative Zoédlogy. What seems to be the same species is 
common in the West Indies, and specimens are in the Museum of Comparative Zoélogy 
from Bermuda, Jamaica, and Tobago; but these West Indian specimens may perhaps 
represent a closely allied species. Whether allied or identical, the West Indian specimens, 
like those from Mer, were found buried in the sand under rock-fragments. They apparently 
live a very sedentary and usually subterranean life. Occasionally individuals are found 
closely attached to the under surface of rock-fragments where these are well buried in sand. 
It is somewhat remarkable that so common and widespread a holothurian has not 
hitherto been described, but it has not been wholly overlooked, for specimens of hypamma 
occur in the type material of Stichopus rigidus Selenka in the Museum of Comparative 
Zoology. This species has long been considered a Holothuria rather than a Stichopus. 
It is superficially much like hypamma, but is easily distinguished by the buttons having 
5 to 8 pairs of holes and the tables being small, with a peripheral circle of holes in a smooth 
disk, and having 8 supporting rods. Selenka obviously confused the two species, as he 
describes the tables of rigida but the buttons of hypamma. The name rigida is to be re- 
stricted to the form with distinct tables, and buttons having 5 to 8 pairs of holes. The 
type locality is the Society Islands. 
Holothuria immobilis. 
Semper. 1868. Holothurien, p. 90, pl. xxix; pl. xxx, figs. 27a, b. 
Although this fine species is recorded from Mauritius, the Philippines, and Samoa, it 
is very little known. It was therefore an unexpected pleasure to find it at Mer, though we 
secured only a single specimen, found on the southeastern reef-flat. It agrees very well 
with Semper’s description. 
Holothuria impatiens. 
Fistularia impatiens Forskal. 1775. Desc. Anim., p. 121, pl. xxxix, fig. B. 
Holothuria impatiens Gmelin. 1788. Linn. Syst. Nat., ed. 13, p. 3142. 
(Plate 19, Figures 3 and 5.) 
Of all holothurians this is, I believe, the most perplexing to the systematist, for it 
displays a diversity of color most unusual in a holothurian, and there is also a lack of con- 
stancy in the development and distribution of papille that causes trouble. Moreover, it 
appears to have a tropicopolitan range, although there are considerable regions where it 
has not yet been taken. No critical comparative study has been made as yet of the cal- 
careous particles in specimens from widely separated areas, nor is anything known of the 
growth-changes in the species. It is not at all improbable, therefore, that several perfectly 
distinct species are now united under the name impatiens. 
