10 HJ. THÉEL, PRELIMINARY REPORT ON THE HOLOTHURIDA. 
with large, not retractile, only a little contractile pedicels, dis- 
posed in a single row all along each side of the ventral surface. 
The odd ambulacrum naked. Bivium with highly elongated, 
flexible, cylindrical, not retractile processes, disposed in a single 
row all along each of its ambulacra. Integument with numerous 
wheel-shaped plates and other calcareous deposits. 
Letmogone Wyville Thomsoni sp. nov. 
Plate I, Figs. 12—13. 
Body much elongated, cylindrical or fusiform, several times 
longer than broad. Tentacles of almost equal size; their termi- 
nal part large, thick and like a sole, destitute of visible pro- 
cesses. Pedicels twenty along each side of the ventral surface, 
large and long; the posterior pairs smaller than the others. Pro- 
cesses of the bivium fourteen along the left, and thirteen along 
the right ambulacra; some of them thirteen to fourteen mm. 
long, rather slender and very fexible; the middle of the back, 
a little behind the tentacles, with a smaller process. Integument 
very thin and soft, with three kinds of calcareous deposits: scat- 
tered spicula, very large, frequently rather straight and unbran- 
ched; large wheels, about 0,16 mm. in diameter, with about 
ten spokes; and smaller wheels, 0,028 mm. in diameter, with 
ten to thirteen spokes, both sorts of wheels concave, the felly 
being directed outwards, not on the same plane as the nave; the 
wheels have somewhat the form of a crown. Between the large 
and small wheels there are many forms, varying much in size 
and shape. 
Colour in alcohol, lighter and darker violet, often inclining 
to dirty brown. Ends of the tentacles leather-coloured. 
Length, 160 mm. 
Breadth, 35 mm. 
Station 300, 1375 fathoms, several specimens. 
Station 147, 1600 fathoms, three specimens. 
In consequence of the great variation of the pedicels and pro- 
cesses, there is scarcely one individual that completely resembles 
another. The individuals from station 147 are distinguished by 
their dark violet colour, continuing to the ends of the tentacles, 
which look almost black. 
