170 THE ECHINODERMS OF TORRES STRAIT. 
radial, are more than half the height; interradial projections sharply pointed, radial blunt; 
interradial pieces slightly concave behind; radial pieces with short but distinct posterior 
prolongations. Polian vessels 4. Madreporic canal single. Genital tubules somewhat 
branched, in a large tuft, each side of the mesentery, near middle of body. 
Calcareous particles consist of tables, supporting rods, and terminal plates. In the 
tentacles are numerous supporting rods, 0.075 to 0.130 mm. long, usually slender and 
unbranched, enlarged and perforated at each end; the smaller ones, however, are often 
deeply forked at one or both ends, the tips being perforated. In the pedicels there are no 
supporting rods, but tables are plentiful and the terminal plates are well developed. In the 
body-wall itself tables are plentiful; they consist of a more or less asymmetrical disk, 
0.047 to 0.094 mm. long, the width one-half to five-sixths as much, perforated with four 
large holes and often with four (or even more) small marginal holes; the spire consists of 
only two rods, the height of which about equals the disk-length. 
Color in life dull purplish, the broad rows of pedicels pale red; in alcohol, the body- 
wall is dull purple, but the pedicels are dirty white. 
Holotype: M. C. Z. No. 1004; under a stone on the flat southwest of Friday Island, 
Torres Strait, September 13, 1913. 
Only a single specimen of this easily recognized holothurian was discovered. The 
broad series of pedicels and the characteristic tables are very distinctive. 
Actinocucumis difficilis. 
Bell. 1884. Alert Rep., p. 148, pl. ix, fig. C. 
The type locality for this species is Albany Island, Torres Strait, and I believe it has 
not been met with since its original discovery. There is no doubt it is very close to the 
following species, but there is no a priori reason why there may not be two species of 
Actinocucumis in Torres Strait, even though we failed, as did Semon, to find any repre- 
sentative of the genus there. If the figures given by Ludwig and by Bell, to show the form 
of the calcareous plates in the body-wall, can be relied on (and they seem well drawn), the 
two writers were not working with specimens of one species. 
Actinocucumis typicus. 
Ludwig. 1874. Arb. Zool-zoot. Inst. Wirzburg, 2, p. 91; pl. vii, fig. 24. 
The type locality for this rare species is Bowen, Queensland, but it is recorded also 
from Amoy and Ceylon. The Challenger took a single specimen at her station 186, which 
was in 8 fathoms of water, Torres Strait. 
Pentacta challengeri. 
Colochirus challengert Théel. 1886. Challenger Hol., p. 80, pl. vi, fig. 11; pl. xiv, figs. 1, 2. 
Three specimens of this Pentacta were taken by the Challenger in Torres Strait, in 
8 fathoms, and the Siboga collected a single specimen near Pulu Jedan at the northeastern 
corner of the Aru Islands. The species is not otherwise known. 
The generic name Pentacta was proposed by Goldfuss in 1820 with only Actinia 
doliolum Pallas from the Cape of Good Hope as its constituent species. This holothurian 
was long lost to science, but in 1887 Ludwig recorded it from Angra Pequena Bay and 
showed that it was identical with an Australian species he had previously described under 
the name Colochirus australis. Curiously enough, however, Ludwig retains the generic name 
Colochirus, dating from 1846, whereas it is obvious that if doliolwm is recognizable as a 
species, it must be the type of Pentacta and hence Colochirus is a synonym of that genus. 
