KEPORT ON THE HOLOTHURIOIDEA. 
117 
(?) Cucumaria turbinata {Labidodesmus), Hutton, 1879. 
HcOntat . — Stewart Island, New Zealand (Hutton). 
Pentacta howcdevskii, Jarzynsky, 1885. 
HcOntat . — White Sea (Jarzynsky). 
Genus 2. Oenus, Forbes, 1841. 
Tentacles ten, two ventral smaller. Ambulacral appendages — pedicels forming a 
simple row along each of the ambulacra, or, at least, along the dorsal and lateral 
ventral ones. Interambulacra, with a single exception, naked. Calcareous ring 
composed of ten simple pieces. Body usually distinctly pentangular, narrow, 
. and the body- wall typically hard from crowded reticulate calcareous scales, or 
from a network almost forminsr a hard shell. 
O 
It seems impossible, for the present, to draw a line of demarcation between the 
genera Oenus and Cucumaria. In several forms referred to Oenus, the pedicels 
do not form simple rows, but are arranged in more or less distinct zigzags, 
which are really nothing but alternating double rows. Considering that Oenus 
vicarius, minutus, lacteus, brunneus, and assimilis do not present any other 
distinctions, they may, without hesitation, be referred to the genus Cucumaria, 
the more so as they present in their general appearance the true Cucumaria- 
type. On the other hand. Semper mentions in his beautiful monograph another 
distinction which seems to be of more value. Thus, those forms should be 
considered as true representatives of the genus Oenus, which were characterised 
by the possession of calcareous scales in the perisome like those known in the 
genus Psolus. Oenus molpadioides, pygmcBus, and imbricatus illustrate such 
forms, and even Sluiter’s Oenus javanicus may be ranked with them, though 
Sluiter points out that no true scales are to be found. These four forms appear 
to have the pedicels in all or most of the ambulacra arranged in distinct simple 
rows. For my own part, I cannot suj^press my doubts as to the validity of these 
generic characters, which may be artificial. Even true CucumaricB are armed 
with scales, though such species are very rare. 
A. Interambulacra naked. 
Oenus 'pygmeeus. Semper, 1868. 
Dor.sal and lateral ventral ambulacra with a simple row, each composed of six to eight 
pedicels. Odd ambulacrum with a double row of about sixteen pedicels. 
Deposits — large scales ; and perforated plane or shghtly concave disks, often 
with four holes shghtly larger than the rest. Calcareous ring of ten pieces, 
the radial with a long bifurcate prolongation posteriorly. 
Habitat . — Bohol (Semper). 
