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THE VOYAGE OF H.M.S. CHALLENGEE. 
IV. Deposits of the body-wall itself in the shape of simple plates. 
TJiyonidium japonicum, v. Marenzeller, 1881. 
Calcareous ring almost like that in the preceding species. Deposits — crowded, 
irregular, perforated smooth plates of variable shape. The pedicels with tables, 
like those in the preceding species, consisting of an irregular curved disk 
supporting a long spine ; in the pedicels of the anterior part of the body, even, 
irregular, perforated plates with rudimentary spire, and, besides, numerous 
small rods (incomplete rosettes) with the dilated ends perforated and branched. 
Habitat . — Japan or China (von Marenzeller). 
This species resembles the preceding one in general shape and other respects. 
V. Deposits of the body -wall itself in the shape of rods. 
Thyonidium schmeltzii, Ludwig, 1875. 
One of the slightly enlarged ends of each of the rods is furnished with spines, the 
other is perforated; for the rest, the rods are smooth. The radial pieces of 
the calcareous ring prolonged into two slender posterior processes, the narrow 
interradial into one ; all these processes composed of several separate pieces 
or joints. 
Habitat . — Bowen and Gulf of St. Vincent (Ludwig), Warrior Eeef and Torres 
Strait (Bell). 
(Mus. Holm.) One very small individual, 12 mm. long, dredged at Pelew Islands. 
. Colour brownish. It possesses the very characteristic deposits, which have 
the outwardly directed slightly enlarged end head-like and spinous, so that the 
rod resembles a club armed with nails. 
The foUc-wing species is too unsatisfactorily known and should be re-examined: — 
Thyonidium ehlersi, Heller, 1868. 
Deposits — tables composed of a round disk perforated with about eight peripheral 
holes and having the margin spinous ; their central spire is made up of four rods. 
Habitat . — Mediterranean Sea (Heller). 
The species is probably very closely aUied to Thyonidivm pellucidum. 
Thyonidium flavum, Greeflf, 1882. 
Deposits — very few disks composed of tightly crowded grains, and, also, scattered 
simple grains. Besides scattered pedicels in the interambulacra, more or less 
distinct double rows are present on the ambulacra. 
Habitat . — Eolas (Greeff). 
The species is not well known. 
