118 
THE VOYAGE OE H.M.S. CHALLENGEE. 
Ocnus imbricatus, Semper, 1868. 
Each of the five ambulacra with a simple row of hard pedicels; each row coHtainmg 
twenty-four to twenty-six pedicels. Deposits — large, overlapping scales ; and 
small rosette-shaped bodies. The ten pieces of the calcareous ring truncated, 
not prolonged, posteriorly. 
Habitat . — Bohol (Semper). 
Ocnus javanicus, Sluiter, 1880. 
Each ambulacrum with a simple row of twenty to twenty-three hard, brittle pedicels. 
Deposits — reticulate spheres resembling those in Colochirus; and an almost 
continuous calcareous network making the perisome very hard. Calcareous 
ring of ten simple pieces, the radial with a bifurcate posterior prolongation. 
Habitat . — Java (Sluiter and Ludwig). 
Neither from the description nor from the figures, drawn by Sluiter, is it possible to 
get a true idea of the shape of the deposits. In the description Sluiter speaks 
of “spheres” like those in Colochirus, and in the explanation of plates he 
enumerates three kinds, viz., “ buttons,” “ tables,” and “ calcareous network.” 
B. Interambulacra with pedicels at the middle of the body. 
Ocnus molpadioides. Semper, 1868. 
Pedicels of the ventral surface longer and more numerous than those of the dorsal. 
Deposits — rounded smaller, and angular larger scales. The radial pieces of the 
calcareous ring with a long bifurcate posterior prolongation. 
Habitat . — China (Semper). 
Genus 3. Echinoeueumis, Bars, 1859 and 1861. 
Tentacles ten, unequal, two lateral much larger than the four dorsal, which in their 
turn are slightly larger than the four ventral. Ambulacral appendages— pedicels, 
arranged in rows on the ambulacra. Interambulacra naked. Integument 
rough. Deposits — crowded, perforated plates with a long spire or spine 
( = tables). 
Echinoeueumis typica, Sars, 1859, 1861. Eupyrgus hispidus, Andrew and Barrett, 
1857. 
Pedicels in alternating double rows along the ambulacra; those on the two dorsal 
ambulacra are much rarer and totally disappear at the middle of the body. 
The tables formed by a large, thin, circular or oval disk, with the numerous 
small round holes slightly smaller near the more or less uneven margin, and 
arranged in rows; the long spire is conical, spinous, and excentric in position 
