. 
Rofe—Actinocrinus, §c. 247 
or uses of these passages; but they appear to give strength to the 
idea suggested by Mr. Sowerby (Zoological Journal, vol. ii. p. 313), 
when speaking of the Blastoidea, ‘that the animal fed on the minute 
beings that abounded in the sea-water, and that it obtained them in 
the manner of Ascidia, by taking them in with the water; and to 
the statement of M. Dujardin, when deseribing Comatula, ‘that the 
ventral surface of the arms and pinne is provided with a double 
range of fleshy tentacula, protected by a double range of fleshy 
lamelle, presenting between them a furrow filled with papille, fur- 
nished with vibratile cilia, by the motion of which animalcula and 
microscopic vegetables are conducted along the arms to the mouth, 
in order to serve as food for the animal.’ It certainly does appear 
more probable that an animal, fixed to one spot, and probably in deep 
water (for, if within the reach of storm-waves, its long branching 
arms would be caught by them with force sufficient to break the 
body from the slender column of attachment), would have to depend 
upon minute organisms abounding in sea-water, rather than upon 
such Crustaceans or Mollucs as might perchance come near it. If 
we assume M. Dujardin’s statement to be correct, the upper pas- 
sages, above described, would be for the supply of food, and of 
water for respiration; whilst the lower served probably for the 
passage of the muscles which gave motion to the arms and their 
appendages, as well as for the connection between the visceral cavity 
and the ovaries, if they were situated in the arms of the Crinoidea as 
in Comatula. 
3. Rhodocrinus. 
The genus Rhodocrinus (Miller), or Gilbertsocrinus (Phillips), is 
not uncommon in this district. Miller appears to have confounded 
a Silurian specimen with the Mountain-limestone genus, and figures 
one from Dudley, which, so far as can be determined from the 
imperfect specimen, was of a different genus. Those, however, 
which he describes from near Bristol are undoubtedly Rhodocrini of 
the Mountain-limestone. This genus differs from most other Cri- 
notdea in the form of the arms and the position of the ovarian aper- 
tures; and in these respects it appears to hold the same relative 
position to them as the Ophiuride do to the Asteriade. The arms 
have no groove on the upper side, but are cylindrical, with a tubular 
canal through the axis; and the ovarian openings are placed imme- 
diately under the base of the arms (figs. 5 and 6). 
The arms vary in size in different species; in some being almost 
equal in diameter to the column or stem; whilst in others they are 
very small. The rarity of specimens with any portion of the arms 
attached, and the peculiar shape and position of the ovarian open- 
ings, have led to these latter being mistaken for the excavation for 
a cuneiforni plate at the base of the arms, as they are at first sight 
very similar to those in Platycrinus and in some species of Cyatho- 
crinus ;* but in a well-preserved specimen from Thorneley there 
* Phillips, in his ‘Geology of Yorkshire’ (Part II., Pl. IV. fig. 25), gives a 
diagram of one set of radial plates in which the ovarian openings, under the base 
of the arms, are clearly indicated. 
