REPOET ON THE HOLOTHHEIOIDEA. 
147 
Thyonidium parviiin, Ludwig, 1881 and 1882. 
The ten pieces of the calcareous ring narrow, slender ; the posterior two prolongations 
of the radial pieces composed of several separate parts or joints. The tables 
are smooth on the margin, consist of an oval disk, as a rule, pierced with eight 
larger peripheral and two smaller central holes, and a spire made up of two 
short rods connected at the top by a transverse beam, the top of the spire 
terminating in about eight spines. 
HoMtat . — Brazil (Ludwig). 
The species is an exception to the rule in having only eighteen tentacles, nine 
larger and nine smaller. 
Thyonidium occidentale, Ludwdg, 1875. 
The radial and interradial pieces of the calcareous ring simple, but between them 
a small calcareous wedge ; the radial having their posterior prolongations short 
and composed of small particles. Tables consisting of a rather well-developed 
perforated disk with uneven dentate margin, and a spire reduced to four short 
spines united at their bases. 
Habitat . — Surinam (Ludwig). 
Thyonidium caudatum [Thy one), Hutton, 1872. 
Body more tapering posteriorly so as to form a narrow caudal portion. Anal teeth 
very rudimentary, made up of a minute calcareous network. Tentacles 
twenty, typically arranged. Pedicels numerous aU over the body, placed on 
low but distinct papUla-hke warts, excepting at the caudal portion, where no 
warts are visible and the pedicels seem to form double rows on the ambulacra, 
the interambulacra being there naked. Calcareous ring, about 30 mm. 
long, is made up of a great number of small pieces, and terminates posteriorly 
in five slender bifurcate prolongations. Anteriorly the interradial parts of 
the ring terminate in a single conical top, the radial in four small teeth. 
Body-wall very rough from numerous larger or smaller tables ; their disks 
are irregularly formed, smooth, elongated, fusiform, three-armed or angular 
with numerous holes, the four central of which are often larger ; their spire 
is in the shape of a long simple conical spine, the base of which seems to be 
composed of two or more rods. Towards the top of the warts the spines 
become more solid and larger. Pedicels supported by such tables and a very 
rudimentary terminal plate. In the caudal portion of the body the disks of 
the tables are elongated, fusiform, and transverse in position. A single 
Polian vesicle and madreporic canal. Colour rusty brown ; caudal portion 
and warts lighter yellowish. Length, 100 mm. or more. Very nearly allied 
to the following species. 
(Mus. Holm). Two type specimens dredged at New Zealand, presented by Hutton. 
