164 
THE VOYAGE OF H.M.S. CHALLENGER. 
the body ; anteriorly, the odd ambulacrum carries only two rows of pedicels. The 
pedicels have a well- developed terminal plate, numerous spinous, curved rods, often with 
the ends perforated, and, besides, a number of four- or three-armed deposits. The 
form of the deposits of the body- wall (PI. X. fig. 21) will be best understood from the 
figures; their diameter is about 0‘056 mm., while the central column has a length of 
about 0'08 mm. In the dorsal processes the deposits often attain a diameter of about 
0*28 mm. The central column mostly terminates in three or four short tops, and it is 
often, especially in the dorsal processes, pierced with one or two holes near the free end ; 
a true “ spire ” is never to be found. I have observed two C-shaped deposits, but they 
probably belong to another animal. 
The calcareous ring is well developed, of the usual shape, without posterior prolonga- 
tions. Two Polian vesicles are present, of which one has a length of 25 mm., while 
the other is rudimentary. The single dorsal madreporic canal is attached to the dorsal 
mesentery. A bundle of very long, slender genital tubes, two or three times dichoto- 
mously branched, is situated on each side of the dorsal mesentery. A single respiratory 
tree with two branches is present, and does not seem to have any intimate connection 
with the pseudhaemal vessels. 
Stichopus (?) torvus, n. sp. (PI. X. figs. 2-4). 
Body cylindrical, with the ventral surface considerably more flattened than the 
strongly convex dorsal surface ; along the Line of junction of the two surfaces the 
body-wall is slightly thickened. Mouth and anus almost terminal, slightly ventral in 
position. Tentacles twenty. The dorsal surface and the lateral parts of the ventral 
surface covered with conical processes, of which those forming a row along the 
transition between the upper and lower surfaces of the body attain a more consider- 
able size and often bear branches ; the processes decrease slightly in size towards the 
middle of the back. The rest of the ventral surface is covered with small crowded 
ambulacral appendages, the form and shape of which are unknown. Calcareous deposits 
totally absent, probably dissolved (?). Colour in alcohol, dirty brown, speckled with 
lighter spots on the back ; tentacles, mouth, and a space round the mouth almost black. 
Length about 210 mm. 
Habitat . — Station 300, December 17, 1875 ; lat. 33° 42' S., long. 78° 18' W.; depth, 
1375 fathoms ; bottom temperature, 35°'5 ; Globigerina ooze; a single specimen. 
The individual I have had at my disposal is so much macerated, wrinkled, and 
covered with foreign matters as to make a detailed examination impossible. Some 
impurity in the alcohol has also probably dissolved the calcareous substances in the 
perisome, in consequence of which it is impossible to state the true shape of the ventral 
ambulacral appendages ; they were either true cylindrical pedicels provided with sucking- 
