Holothuroidea from Southern Chile — PAWSON 
Pseudo onus dubiosus (Semper), 1 specimen 
Neopsolidium convergens (Herouard), 2 
specimens 
Trochodota purpurea (Lesson), 1 specimen 
SYSTEMATIC ACCOUNT 
Order DENDROCHIROTIDA 
Family PHYLLOPHORIDAE 
Subfamily THYONIDIINAE Heding and 
Panning, 1954 
Genus Athyonidium Deichmann, 1941 
Eucyclus Lampert, 1885, p. 920; Theel, 1886^, 
p. 268; Ludwig, 1887, p. 1239; Heding and 
Panning, 1954, p. 36: name preoccupied. 
TYPE SPECIES: Athyonidium chilensis (Sem- 
per). 
REMARKS: This genus is monotypic. Deich- 
mann (1941) pointed out that the generic 
name Eucyclus was preoccupied, having been 
claimed some years earlier for the Mollusca. 
Heding and Panning ( 1954) unfortunately per- 
sisted with the old generic name. 
Athyonidium chilensis (Semper) 
Thy one ( Stolus ) chilensis Semper, 1868, p. 241, 
pi. 40, figs. 3-6; Lampert, 1885, p. 156. 
Eucyclus duplicatus Lampert, 1885, p. 250; 
Theel, 1886^, p. 268. 
Thy one chilensis Theel, 1886^, p. 139. 
Phyllophorus chilensis Ludwig, 1886, p. 24. 
Athyonidium chilensis Deichmann, 1941, p. 127. 
Eucyclus chilensis Heding and Panning, 1954, 
p. 36, fig. 2. 
DIAGNOSIS : Large forms (25 cm ) with thick, 
soft skin and numerous stout feet. Tentacles, five 
large external pairs and five small inner pairs. 
Calcareous ring with five stout, almost rectangu- 
lar radials and five insignificant interradials, 
often completely concealed in surrounding tis- 
sue. One large dorsal stone canal, often branched, 
and one or two tufts of smaller stone canals with 
minute heads. Numerous tufts of branched 
Polian vesicles. Inner anatomy otherwise typical 
of the family. 
Deposits large, well-developed end plates, a 
few perforated spinous rods; tentacles with few 
455 
rosettes in younger individuals. Colour greyish 
mottled to almost black, ventrum paler, tentacles 
dark. Shallow-water forms. (After Deichmann, 
1941.) 
MATERIAL EXAMINED: Sta. 4, four specimens 
from Macro cystis zone. 
REMARKS: The four specimens in the present 
collection range in length between 140 mm and 
185 mm. The body is covered in tube feet, which 
are more numerous ventrally. Colour in alcohol 
is dark brown to blackish dorsally, fading to 
light brownish-grey on the ventral surface. There 
are 20 black tentacles arranged in two rings. The 
outer ring has 10 regularly spaced, profusely 
branched larger tentacles, averaging about 25 
mm in length. The inner ring lies dose around 
the mouth, and comprises five radially placed 
pairs of short, sparsely branched tentacles of 8 
mm average length. The oral field is about 20 
mm in diameter. Immediately outside the ring 
of large tentacles, in the middorsal interradius, 
lies a small approximately circular mound of 
tissue about 1 mm high and 2 mm broad, which 
supports the genital aperture. 
The mouth is large, and examination of 
the intestinal contents in a dissected specimen 
showed that hard pieces of Macrocystis stipe up 
to 42 mm long and 6 mm wide, or 25 mm X 10 
mm can be ingested. The intestine also contains 
fragments of green algae, both filamentous and 
thalloid, brown algae (predominantly Macro- 
cystis ), appendages of small crustaceans, and 
hydroids. This species seems to be primarily a 
vegetarian browser. 
The calcareous ring is large, and has been 
illustrated by Heding and Panning (1954). 
The gut is thin-walled, and takes a large 
S-shaped loop. The cloaca is broad, thick-walled, 
attached to the body wall by very numerous 
muscle strands. Respiratory trees take the form 
of two broad flat tubes with scattered, profusely 
branched tufts of respiratory tubules. The trees 
arise from the anterior end of the cloaca in the 
lateral dorsal interradii, and extend anteriorly 
for about half the length of the body cavity. 
A tuft of numerous Polian vesicles arises from 
the ventral side of the water-vascular ring. The 
stone canal stems from the dorsal side of the 
ring, and gives off smaller canals which lie to 
each side of the strong dorsal mesentery, and 
terminate in nodular madreporites. 
