130 
THE VOYAGE OE H.M.S. CHALLENGER. 
Psolus squamatus, by its small size and by having distinct oral and anal valves, and 
only tvFO rows of pedicels around the sole. Its affinity with the two following 
species is much more apparent, and is such that it is almost impossible to draw 
a hne of demarcation between them. Compare the above description. 
Psolus operculatus [Cuvieria), Pourtales, 1868, 1869. Lepidopsolus (?) operculatus, 
Verrill, 1867-1871. 
Body oval, flattened, covered with flnely and sparsely granulated scales, very 
■ compactly imbricated, but overlapping very little excepting near the mouth and 
anus. Oral aperture closed by flve large triangular scales, alternating with and 
• covering five narrow, tooth-shaped ones. Anus closed in the same way, but the 
scales are much less regular and constant. A double row of pedicels surrounds 
the soft sole, those of the outer row perforating the marginal plates ; sometimes 
two or three pedicels are present anteriorly in the odd ambulacrum. 
Habitat. — Sand Key and Florida Reefs (Pourtaffis). 
The species is doubtless nearly allied to Psolus squamatus, and appears to differ from 
it mainly in having larger, more regular oral valves, and in having only two 
rows of pedicels around the sole. Pourtalfes does not describe the armature 
of the sole. 
Psolus antarcticus {Cuvieria), Philippi, 1857; Semper, 1868; Studer, 1877; Bell, 1882. 
Lepidopsolus (?) antarcticus, Yernll, 1867-1871. 
Habitat. — Strait of Magellan (Philippi, Studer), Portland Bay and Cove (Bell). 
According to Philippi, this species is nearly related to or identical with Psolus 
squamatus. Bell says that the body is much more flattened than in the last- 
mentioned form, and that the oral and anal valves are very much larger and 
more regularly arranged. Indeed, the oral valves consist of five large 
triangular scales, and the anal ones are also five but smaller. The scales 
covering the dorsal surface are large, so that only about five (Philippi) or ten 
to eleven (Studer) are placed between mouth and anus ; they are also much 
less granulated or nearly smooth. Round the margin of the dorsal surface 
the scales are much .smaller. Only a double row of pedicels is present round 
the sole. The deposits in the sole have not been described. 
2. Dorsal integument without scales [f). 
Psolus poriferus (Cuvieria), Studer, 1877 and 1879. 
Dorsal surface furrowed, so as to present irregular poriferous spaces. Round the 
margin, however, poriferous scales seem to be present. 
Habitat. — Royal Sound, Kerguelen (Studer). 
The description given by Studer is very summary and unsatisfactory. The species is 
possibly identical with Bell’s Psolus ambulator. 
