172 THE ECHINODERMS OF TORRES STRAIT. 
0.040 mm. wide, and heavy terminal plates. Tentacles with big supporting rods (pl. 37, 
fig. 3), 0.400 mm. long by 0.050 wide, in the main stem and very numerous smaller rods 
in the branches; in the ultimate branchlets the rods (pl. 37, fig. 2) are about 0.040 mm. 
long and scarcely 0.002 mm. wide; besides the rods the basal part of the tentacles contains 
numerous rosette-like, perforated plates only 0.030 to 0.040 mm. across. 
Color in life, dull purplish-brown; in alcohol, very pale brown, the tentacles much 
darker yellowish-brown. 
Holotype: M. C. Z. No. 997, from under surface of a rock-fragment, southeastern 
reef-flat, Mer, Murray Islands, Torres Strait. 
This little holothurian was not distinguished from Pseudocucumis aciculatus when it 
was found, as its color and habitat were like those of some small specimens of that species. 
Of course, the more careful examination with the microscope soon showed the great dif- 
ferences. While it is not impossible that this individual may prove to be a young one of 
some previously known species, or even identical with Ludwig’s little species (minuta) 
from Bowen, Queensland, the calcareous particles seem to be quite distinctive, and it has 
seemed wiser to record it under a new name. The genus Pentacta very much needs critical 
revision, and a careful study of growth-changes in the calcareous deposits of the body-wall 
will probably show that too many species are now recognized. The corresponding changes 
in the character and distribution of the ambulacral appendages and interambulacral 
papille are also much in need of critical study. 
HOLOTHURIIDEE. 
Labidodemas semperianum. 
Selenka. 1867. Zeit. f. w. Zool., 17, p.£309, pl.3xvii, figs. 1-3. 
Although Selenka gives ‘‘Sandwich Islands” as the type locality for this interesting 
holothurian, his types in the Museum of Comparative Zoélogy are from the Society Islands. 
While it is possible that the specimens in the Museum Godeffroy are from the Hawaiian 
group, there are no other records from there, and I think ‘‘Sandwich Islands”’ is a slip of 
the pen. I agree with Sluiter (1901) that selenkianum Semper and dubiosum Ludwig are 
synonyms of Selenka’s name. But I can not feel that Sluiter’s L. egestosum is a valid 
species, for I think the entire absence of caleareous matter demonstrates that the formalin 
in which the specimen was preserved was the cause of its peculiarities. The fact that other 
bolothurians in the same receptacle were not decalcified proves nothing, as it is unlikely 
all were put in at the same time, and moreover formalin acts to different degrees on 
different specimens under apparently similar conditions. If egestoswm, therefore, is a 
Labidodemas and not a young Holothuria, it must, I think, be considered identical with 
sempertanum, which was also found on the reef at Saleyer. 
This species occurs at Tahiti, at the Fiji Islands, at half a dozen stations in the East 
Indies, and at the Andaman Islands. I took a small specimen, about 50 mm. long, ‘‘pellucid 
white” in color, on the reef at Papeete, Tahiti, August 5, 1913. At Mer, three specimens 
were found buried in the sand, under rocks, on the southeastern reef-flat. They were 200 
to 250 mm. long in life, and about 25 mm. in diameter. The color was a delicate trans- 
lucent pink and the papille and pedicels were notably long. Of course, the preserved 
specimens are much smaller and more opaque. 
Holothuria altimensis! sp. nov. 
(Plate 37, Figures 20 to 29.) 
Length 20 mm.; diameter about 7 mm.; body somewhat depressed, the distinct 
ventral surface flattened. Tentacles 20, well extended and somewhat rigid from the abun- 
1 Altus =high+mensa=a table, in reference to the very high spires with which the tables are provided. 
