Holothuroidea from Southern Chile — PAWSON 
459 
knobbed buttons (0.9 mm average length). Tube 
feet with rudimentary end plates or none at 
all, and numerous perforated supporting rods, 
mostly three-armed. Introvert and tentacles have 
perforated plates and rods. (After Deichmann, 
1941.) 
MATERIAL EXAMINED: Sta. 19, 1 specimen; 
Sta. 27, 57 specimens; Sta. 39, 15 specimens; 
Sta. 40, 2 specimens; Sta. 52, 10 specimens; Sta. 
54, 4 specimens; Sta. 77, 1 specimen. 
remarks: The 90 specimens range in length 
from 10 mm to 50 mm. The colour varies be- 
tween white and pink. This species is one of the 
best-known from Chile and has been described 
by many workers. Panning (1950, 1952) has 
suggested that there are three "forms” of this 
species. They are P. dubiosus-leonina, from the 
southern end ‘of South America (all of the pres- 
ent specimens are of this type); P. dubiosus- 
duhiosa ranges the Atlantic and eastern Pacific 
shores, as far south as Chile; P. dubiosus-jageri 
is known from South Africa. 
The deposits of the body wall in the present 
material (Fig. 1 ,5,7) are those of the leonina 
form. Small specimens may show stages in the 
development of knobbed buttons (Fig. 1, 8). 
The tube foot deposits (Fig. 1, 4) are perforated 
plates, often three-armed, about 0.22 mm in 
average length. The tentacles contain perforated 
rods and small plates up to 0.32 mm long (Fig. 
1 , 6 ). 
A thorough investigation of all of the species 
in the genus Pseudocnm is urgently needed, par- 
ticularly those species which have the body wall 
deposits as plates with one end denticulate, and 
buttons. For a successful attempt at a revision, 
a representative range of specimens of each 
species would be required, and unfortunately 
these are not available to the writer at the pres- 
ent time. 
DISTRIBUTION : The leonina - form of this spe- 
cies is known from southern Peru in the west of 
South America to the Rio de la Plata in the east, 
and the Falkland Is., from the intertidal zone to 
approximately 100 m. 
Subfamily Colochirinae 
Genus Tr achy thy one Studer, 1876 
For synonymy, see Panning (1949). 
DIAGNOSIS: Calcareous ring simple, without 
forked processes. In the skin are cups and smooth 
plates, the plates imbricating in some species. 
(After Panning, 19490 
TYPE SPECIES: Trachythyone muricata (Stu- 
der). 
remarks: This genus comprises about 20 
species, of which 1 1 are distributed in the south- 
ern Pacific Ocean from Australia to South Amer- 
ica and also Kerguelen Is. The remaining species 
are found in the Indo- west-Pacific and Medi- 
terranean regions. 
Trachythyone lechleri ( Lampert ) 
Thyone lechleri Lampert, 1885, p. 253, fig. 64; 
Theel, 1886a, p. 267; Ludwig 189 8a, p. 44, 
pis. 2, 3, figs. 26-33; Perrier, 1905, p. 35; 
Ekman, 1925, p. 101, fig. 22; Deichmann, 
1947, p.335. 
Thyone hassleri Theel, 1886b, pp. 11-12. 
Trachythyone lechleri Panning, 1949, p. 426, 
figs. 12-14. 
DIAGNOSIS: Medium-sized (up to 15 cm total 
length); colour in alcohol, brown. Tube feet 
numerous, scattered. Deposits thick oval plates, 
sparsely perforated, length 0.07-0.2 mm, over- 
lain by rudimentary "cups” of varying shapes. 
End plates in tube feet surrounded by perforated 
supporting plates of 0.2 mm average length. 
MATERIAL EXAMINED: Sta. 54, nine speci- 
mens. 
remarks : These are typical specimens of this 
unusual species. The total length ranges from 
47 mm (a strongly contracted specimen) to 130 
mm. The colour in alcohol is mottled light 
brown to dark orange-brown. The tube feet are 
lighter in colour than the rest of the body. In 
most cases the tentacles are completely retracted. 
The calcareous ring is simple, with no pos- 
terior processes, and is solid, with the five radials 
and five interradials firmly fused together. The 
Fig. 1 . 1—3, Cladodactyla crocea (Lesson). 1, Tentacle deposits. 2, Dorsal tube foot end plate. 3, Dorsal 
skin deposits. 
4—8, Pseudocnus dubiosus (Semper). 4, Tube foot deposits. 5, Knobbed plates from the skin. 6, Tentacle 
deposits. 7, Knobbed buttons. 8, Developing knobbed buttons. 
