48 
frequently met with specimens in that state, but as yet have never seen any side 
arms clasping round extraneous matter. 
The Couumn. (Pu, 1. and Pt, 11. fig. 24. and 26.) The place where the late 
J. Tonin’s, Esq. specimen broke off, was in a part of the column where its 
joints had acquired a degree of maturity, and the fracture goes slantingly 
through several of them, thereby demonstrating the smal! quantity of membrane 
intervening between them, its tenacity, and also the thinness of the exterior 
integument that surrounds the joints, which is now so dried up as to be al- 
most imperceptible, being of a pale yellow, and intimately connected with 
the calcareous laminar secreted matter forming them. As the column is not 
broken in such a manner as to afford a correct idea of the adhering surface of 
the joints, I must refer for this point to the fossil remains of this species occur- 
ing in the lyas. ‘The alimentary canal and its investing membrane are very 
small: ‘The shape of the column being pentangular, and more or less indented 
between the five salient angles. (Pu. 1. fig. 24. and 26.) We trace on the in- 
ferior and superior surface of each columuar joint five subovate petal-like 
figures, marked by elevated ridges radiating round the margin of each of them, 
the interior of each of these five petal-like figures forms an oblong, ovate, 
smooth space, surrounded by the marginal radii, opening by a narrow groove 
at the inner end, which is the most pointed, into the alimentary canal. On 
joints not fully formed there is also a depression proceeding from the alimen- 
tary canal, between the marginal radii surrounding the sides of the contiguous 
petal-like division, to a smooth space beyond them, filling up the more or less 
indented, ‘and frequently contracted, intervals between them. If we consider 
this construction in an early state of growth, when the joints are very thin and 
muscular, and the calcareous secretion is only commencing, and hence follow 
the operation of nature, we may suppose that the calcareous deposit first 
formed round the alimentary canal, in the space occupied by the five petal-like 
divisions and their marginal radii, and thus continues to increase till the joint 
has acquired a thickness consistent with the proportions and size of the animal. 
The space between the five petal-like divisions continues muscular a consider- 
able time longer, and begins only at a later period, and very gradually, to se- 
erete calcareous matter to strengthen the deposit round the alimentary canal, 
and to interpose thin layers to keep apart the petal-like divisions. The thin 
muscular ingegument investing the alimentary canal, probably forms a sphiné- 
ter at the junction of each two. joints, dividing here into ten conspicuous por- 
tions or muscular integument, one extending to each of the spaces between 
