MESSES. P. MAETIN DUNCAN AND H. M. JENKINS ON PALiEOCOEYNE. 695 
at the extremity of the crateriform process, whose sides are marked with radiating lines 
very much like the margins of the oral plates in young Pentacrini *. It would appear 
that this projection depended upon the condition of the nutrition of the animal before 
its entombment. 
The tentacular canals diminish in size with the length of the processes, and they are 
not continuous with the irregular spinules ; but whenever the distal end of a long ten- 
tacle can be examined, a small central puckering is observed on it. It is very probable 
that the cavity of the tentacular process was continued into a soft and ciliated prolon- 
gation through this orifice. The union of the tentacular canals with the cavity of the 
body produces, in transverse sections of that part of the animal, an appearance like that 
of the rosette in the Crinoidea. 
Transverse and longitudinal sections of the stem show the papillary and faintly 
spinose and pitted ornamentation of the outside of the hard parts, and delicate striae 
running from the inside externally and horizontally, but there is nothing like an open- 
ing between the large internal cavity and the outside to be seen. 
The base is formed of the external hard tissue which grasps and includes its own cel- 
lular structures and those of the Polyzoon. Its length varies. 
III. Zoological position. — The absence of any structures resembling basal or baso- 
radial plates and of joints in the tentacular processes, renders the opinion that the fossil 
should be referred to the Echinodermata untenable. 
The isolation of the individuals, each possessing but one external opening, and the 
general characters of the tentacular processes, preclude any reference to the Polyzoa. 
The internal anatomy, the structure of the hard parts, and the nature of the tentacular 
processes, prevent classification with the Zoantharia. 
Were it not for the calcareous investments, there would be no difficulty in admitting 
the fossil amongst the Hydrozoa ; and had we not been able to avail ourselves of the 
affinities of the very anomalous genus Bimeria (Wright) the difficulty could hardly 
have been overcome. 
There are many kinds of periderm amongst the recent Tubularine Hydrozoa, and the 
genera Monocaulos (Allman), Gorymorpha (Allman), Eudendrium (Ehren.), and Bimeria 
(Wright), afford examples of a gradation in structure from a condition of great tenuity 
and delicacy to one of a chitinous character, and up to the peculiar pergamentaceous 
nature of the polypary of the last-named genus. 
But the coenosarc of Monocaulos , Gorymorpha , and Eudendrium is the only part 
covered by the periderm. In the genus Bimeria , however, the semi-solid investment not 
only covers the coenosarc, but is also continued over the greater part of the tentacles and 
over the upper part of the body, leaving an opening for the mouth on the metastome. 
The resemblance of the fossil under consideration to the trophosome of Bimeria 
vestita (Wright) is very decided. 
* Researches on the Structure, Physiology, and Development of Antedon ( Comatula , Lamk.) rosaceus. By 
William B. Carpenter, M.D., F.E.S., Phil. Trans. Eoy. Soc. vol. clvi. p. 671. 
4 Z 2 
