CHAP.) THE DEEP-SEA FAUNA. 439 
intermediate joints is complete. At the top of the 
stem five little calcareous lumps lke buttons stand 
out from the projecting ridges, and upon these and 
upon the upper part of the stem the cup which 
holds the viscera of the animal is placed. These 
buttons are of but little moment in this form, but 
they represent joints which are often developed into 
large, highly-ornamented plates in the various tribes 
of its fossil ancestors. ‘They are called the ‘basal’ 
plates of the cup. Next, in an upper tier, alternating 
with the last, we have a row of five oblong plates 
opposite the grooves of the stem, and all cemented 
into a ring. ‘These plates are separate when the 
animal is young; they are called the ‘first radial’ 
plates.. They are the first of long chains of joints 
which are continued to the ends of the arms. Imme- 
diately above these plates, and resting upon them, 
there is a second row of plates nearly of the same 
size and shape, only they remain separate from one 
another, never uniting into a ring. These are the 
‘second radials,’ and immediately upon these rest 
a third series of five, very like the plates of the 
other two rows, only their upper surfaces rise into 
a cross ridge in the centre, and they have the 
two sides bevelled off like the eaves of a gable, to 
admit of two joints being seated upon each of them 
instead of one. ‘This last ring of joints are the 
‘radial axillaries,’ and above these we have the first 
bifureation of the arms. These three rings of 
radial joints form the true cup. In the modern 
species they are very small, but in many fossils 
they acquire a large size, and enclose, frequently 
with the aid of various rows of intermediate or 
