EEPORT ON THE HOLOTHHRIOIHEA. 
143 
white colour, possibly a result of the alcohol, with dark tentacles, and has only 
one PoHan vesicle (madreporic canals unknown) ; Thyone saccllus is of a dark 
brown colour, has four Polian vesicles and twelve to twenty madreporic canals. 
Stereoderma validum, Bell, 1884. 
Habitat . — Port Jackson, North Dunbar Island, China Sea (Bell), between Ball’s Head 
and Goat Island, Brisbane 'Water (Bell). 
So far as I can find out from the description of Bell, this form cannot be anything 
else than a Colochirus spinosus, Quoy and Gaimard. Evidence of the correctness 
of this view is to be found in the form of the body, the presence of the char- 
acteristic conical denticulate prominences on each side of the ventral surface, the 
calcareous ring and even the general appearance of the calcareous deposits, 
though it may be observed that Bell does not mention anything about the 
presence of reticulate scales in the forms examined by him. Thus, if 
I am right in my supposition, Stereoclerma murrayi is a Thyom sacdla and 
Stereoclerma validum a Colochirus spinosus. Pinally, I feel convinced that 
further examinations will prove that Stereoclerma unisemita may be referred to 
some already well-known genus, for instance Thyone. 
Genus 11. Thyonidium, Diiben and Koren, 1844. 
Tentacles twenty, exceptionally fetver or more ; five pairs of larger alternating with 
five pairs of smaller. Ambulacral appendages in the shape of pedicels, some- 
times densely crowded, sometimes more thinly scattered ; often an arrangement 
of them in rows distinguishable along the ambulacra. 
1. Deposits of the body- wall itself, none, or present in the form of 
tables or plates in the neck portion alone. 
Thyonidium drummondii [Holothuria), Thompson, 1840 ; Sars, 1861. Cucumaria 
drummondii, Forbes, 1841. Cucumaria communis, Forbes, 1841. (?) Thyone 
portlocldi, Forbes, 1841. Thyonidium commune, Dllben and Koren, 1844. 
Holothuria fusus, (Ersted, 1833 (according to Diiben and Koren). Thyonidium 
diibeni, Norman, 1868. 
Habitat . — Scandinavian coasts from the Sound to Lofoten (Sars, MAndiew and 
Barrett, Danielssen, Diiben and Koren, Liitken), British Islands (Thompson, 
Hodge, MTntosh, Forbes, Norman). 
(Mus. Hohn.) Several specimens from the west coast of Sweden and Norway. So 
far as I can see, this species must be nearly allied to Thyonidium pellucidum, 
