246 
that one of but medium thickness is placed between two thin ones, 
which again are comprised between two of more than ordinary thick- 
ness, the thinnest of all being interposed between each of the preceding 
articulations. Round the thickest of these asteriae are placed 
five little pits, evidently intended for the insertion of lateral pro- 
cesses. 
From similar changes in the arrangement of pentagonal asteriae, 
from the intermixture of those differing in thickness, and the disposi- 
tion of their ornamental protuberances, great variety arises. Some 
specimens are figured by Rosinus as being remarkable, from their asteriae 
being joined together in an anomalous manner ; the lines of articula- 
tion, in some, assuming somewhat of a spiral twist ; whilst, in 
others, additional lines appear irregularly to intersect and divide 
the asteriae in various directions. Some of these differences appear 
to be the effect entirely of injury from violence, inflicted either dur- 
ing the life of the animal, or whilst passing from the animal to the 
mineral state ; but others may properly be regarded as sports of na- 
ture. 
The sides of the asteriae, forming the column. Fig. 54, is marked on 
its sides by transverse lines of points, gradually diminishing in size, 
from the centre of the line, and differing in their length, and even their 
arrangement, in different columns. In the column. Fig. 55, each star- 
stone is adorned by a line of minute projections, placed on each angle of 
the star, and extending each way about one-eighth of each side. 
The whole surface of the column is thus made to assume a richly embossed 
appearance, to which the conspicuous appearance of the crenated line of 
articulation much contributes. 
The column. Fig. 56, has a still more elegant appearance. The pat- 
tern of its ornament may be seen to comprise five of the asteriae ; the 
uppermost, lowest, and most projecting of which are encircled by a 
line which, swelling boldly in the middle of the sides, terminates in 
a round point on the angles themselves. Next to each of these is an 
