CRINOID FROM THE SOUTHERN SEA. 
925 
be associated with the Rhodocrinidce rather than with the Actinocrinidce to some of 
which {e.g., Melocrinus) it would be allied, owing to the presence of a tetramerous base. 
Wachsmuth and Springer point out that “no Actinocrinoidhas ever been discovered 
in which the interradial field, except at the azygous side, extends to the basal disc.” 
But Miller’s description, which is borne out by his figures (one of which is repro¬ 
duced in Plate 71, fig. 8), runs as follows : “ The azygous area is remarkably large, and 
covered in the central part by a vertical series of plates having about the same size as 
the regular radial series, and upon each side of the vertical series there is a depressed 
area covered by small plates having a tubercle in the central part, as in the regular 
interradial areas. There are seven plates, each having a length about twice as great as 
its width, in the vertical series, from the basal plate upon which the series rests to the 
top of the vault. This vertical series is continued to the top of the proboscis, and 
contains in its entire length more than fourteen plates. It has such strong resem¬ 
blance to the radial series, except as to the branching at the secondary radials, that 
the general appearance of the body is that of a species having six radial series.” 
There can, I think, be no reasonable doubt that the anal appendage of Thaumato- 
crinus, although free laterally, owing to the simplicity of the rays, is homologous with 
the vertical series of plates in the anal interradius of Reteocrinus and Xenocrinus; 
and it is not a little curious to find a character which died out some time before 
the Mesozoic epoch recurring in a recent Comatula. I am quite at a loss as to 
the probable function of this anal appendage in Thaumatocrinus, but it seems to differ 
from that of the Palaeocrinoids in one point, for Miller describes it in Xenocrinus as 
continued to the top of the proboscis, which is not the case in Thaumatocrinus. The 
lower part of the anal tube bears plates, but they are continuous with those covering 
the disc over which the anal appendage arches, without, however, forming any 
connexion with the plates in question. 
It is difficult to consider the existence of interradials and of the anal appendage of 
Thaumatocrinus as instances of atavism, for no known Neocrinoid presents any similar 
characters, and it is a long way back from a recent Comatula to a Palaeozoic 
Crinoid. The appendage soon disappeared, both the genera possessing it being of 
Lower Silurian age ; but Crinoids with the interradials resting on the basals persisted 
into the Carboniferous period, and possibly also some with an anal appendage. No¬ 
thing of the kind is visible, however, in any genus of Neocrinoicls, so that the 
reappearance of these characters in such a specialised type as a Comatula, is not a 
little surprising. Associated with them we find the distinctly embryonic characters 
of persistent basal and oral plates, the latter occurring in no other Comatula , together 
with the simplicity of the undivided arms. 
Thaumatocrinus is thus a type of unusual interest, and should be sought for 
carefully in any future deep-sea explorations. It is evident that the possibilities 
of the abyssal fauna are by no means exhausted yet. 
The presence of the oral pyramid in Thaumatocrinus, as in Hyocrinus, suggests the 
MDCCCLXXXIII. 6 C 
