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rayed circular plate (PL YI. fig. 8) which rests on the middle of 
the upper surface of the centrodorsal piece so as to cover in 
the chambered organ above. (PI. Y. fig. 1, ro.) It is lodged 
in the lower part of the funnel formed by the first radials, 
which now rest directly on the centrodorsal, and it becomes 
more or less closely united to their inner ends, so that when 
the circlet of radials is separated from the centrodorsal, the 
rosette comes away with it. This is shown in PL YI. fig. 6, 
representing the under surface of the radials of Antedon celtica 
with the rosette (ro) in the centre of the ring formed by them. 
This metamorphosis of the basals of recent Comatulce into a 
concealed rosette is a very singular circumstance, because it 
shows that the Comatulce have, as it were, taken a new departure, 
and have branched off from the type of Pentacrinus in the 
resemblance of which they have developed. In all the recent 
Pentacrinus species and in most of the fossil ones the radials are 
cut off from the top stem- joint by a more or less complete ring 
of basals. (Pl. YI. fig. 3, b.) These basals are sometimes small, and 
only just in contact by their central ends, while their outer ends 
appear externally as small buttons separating the radials from the 
top stem- joint at the angles of the calyx. There is every gradation 
between this condition and that in which they meet one another 
all round, so that the radials rest entirely upon them, and are 
nowhere in contact with the stem- joint ; but we know of no 
recent Pentacrinus in which the basals do not appear externally, 
though some of the fossil forms are in this condition. On the 
other hand we have no certain knowledge of any fossil Comatulce 
with a rosette. The earliest known Comatulce occur in the 
Inferior Oolite of this country. Figs. 4 and 5 on Pl. YI. are 
two views of the calyx of one of them, Ant. cheltonensis. The 
difference between them and figs. 6 and 7, which represent the 
corresponding parts of a recent species, is at once apparent. In 
the fossil the basals form a five-pointed star, lying beneath the 
under-surface of the radials (fig. 5) ; while in the recent species 
all that remains of them is the inconspicuous rosette occupying 
the gap between the inner ends of the radials (fig. 6). 
The Oolitic rocks of South Germany and of Switzerland, 
which are of approximately the same geological age as the 
Oxford Clay and Coralline Oolite of the British area, contain 
several different kinds of Comatulce , far more than are known 
in this country. Fig. 9 on Pl. YI. represents the calyx of one of 
them, Ant. scrobiculata. 
All the Oolitic Comatulce have basal pieces like those of this 
species and of Ant. cheltonensis (figs. 4, 5), though they are not 
always so large. In some forms they do not appear at all on 
the outside of the calyx, so that they are only visible in speci- 
mens from which the centrodorsal has been removed. This is 
