Revision of the Holothurioidea. 345 
retaining the minute organisms upon which it feeds. MICHAILOVSKIJ, 
1902, briefly describes tentacular spicules. 
Formless deposits. — Within the inner half of the body- 
wall are often found the formless deposits which Düsen & Koren, 
1846, 1846a, describe and figure as „irregular conglomerated calcareous 
lumps“. DüÜBENn & Kork declare these as the only spicules of the 
body-wall in this species. In accord with MicHALovskrs, 1902, 
1904, I find these formless deposits in the deepest layers of the 
body-wall of some individuals. 
Anal teeth. — One anal tooth is found at the posterior 
termination of each mid-radial line just beyond the bases of the 
last pair of pedicels (Pl. 13, Fig. 20). 
The anal tooth is small, 0,9 mm long and 0,6 mm wide at its base, 
and probably for that reason has hitherto been overlooked. The 
free point of the tooth projects posteriorly, slightly above the perianal 
surface just outside of the thickened rim of the anus (Fig. 20). 
Under a magnification of 420 diameters the anal tooth is seen to 
be constructed in the same manner as the perforated plate and 
seems as if made up of layers of such material interwoven to form 
the well defined tooth. Of the 60 holothurids examined for this 
character, 58°, have the 5 anal teeth clearly marked while in most 
of the others, owing to contraction of the body-wall, their presence 
is not determinable. In two cases the teeth are lacking. Even in 
the very young, where the anal teeth are well marked they are 
comparatively small, not funetional, and hence, in this species, must 
be regarded as vestigeal structures. 
Presence or Absence of Spicules. — Lürken, 1857, and 
SEMPER, 1868, describe the perforated plates as only near the 
pedicels. TrX£EL, 1886, remarks that the plates are rare in old 
specimens and usually he finds them only in the pedicels, or in their 
neighborhood; while in very small forms, when present in all parts 
of the holothurid, the spieules are more crowded in the ambulacral 
appendages. Sometimes the spicules are entirely lacking in both 
young and adult specimens. SELENKA, 1867, finds no plates and „only 
very minute arragonite needles“ which must have been of foreign 
origin as shown by SEMPER, 1868. 
In order to determine the presence, or absence, of spicules, and 
their distribution when present, I have carefully examined 46 
specimens, 56 being adult. Of these 15 adults, and 9 young, have 
the typical spicules in the body-wall, pedicels and tentacles. ranging 
