190 Dr. J. Anderson on an apparently new Form of Holothuria. 
in a small shallow vessel of sea-water, with only a little piece of 
sea-weed in it to keep the water in good condition. During by 
far the greater part of the nineteen months of its confinement 
it remained contracted, seldom moving from one spot. The 
only food it could possibly have obtained must have consisted 
either of microscopic animalcules or the spores of Alge. The 
animal is still alive; and I am therefore not in a position to say 
anything regarding its internal structure. 
The dorsal region of the body, when the creature is contracted, 
is of a deep purplish-brown tint, but the ventral surface is of a 
paler hue. The dorsal surface, when the creature is distended, 
approaches very much to the colour of the ventral aspect when 
in a state of contraction. 
When contracted, it is little more than a quarter of an inch 
in length, and about the fifth of an inch in breadth; but when 
distended and moving about, it becomes double this length, and 
its breadth also is slightly increased. 
The five double rows of sucking-feet are unsymmetrical, the 
two dorsal rows being irregular in their distribution. The dorsal 
feet are much less numerous than the ventral, which they greatly 
exceed in size, and from which they differ very much in their 
undilated tips, and by their being seated in some instances upon 
rounded eminences or tubercles of considerable size. These feet 
are capable of complete retraction into the tubercles. Though 
the two dorsal rows of feet differ very much from the ordinary 
arrangement of these organs in the Holothuriade, we can never- 
theless trace faint indications of the double character of the 
rows. 
The three double rows of ventral sucking-feet are fully deve- 
loped; the feet are placed opposite to one another, and are 
dilated at their tips, but are only partially retractile. The ani- 
mal walks upon the three well-developed rows; and if turned 
upon the aborted ones, it immediately recovers itself, and turns 
round to what appears to be its ventral surface. In the anoma- 
lous genus Psolus, as is well known, the locomotive organs are 
restricted to a small flattened ventral disk, on which the three 
developed rows of feet are disposed. 
The arrangement of the feet in the animal under considera- 
tion is another instance of a like specialization of function, 
and indicates the tripod nature of the Holothurie. Viewed 
thus, this little animal is fraught with interest, and may serve 
to connect, by its gradation of form, the genus Holothuria, with 
its five well-developed rows of locomotive feet, and the genus 
Psolus. 
The tentacles (Pl. XI. fig. 2) are ten in number; eight of them 
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