CALYPTOCRINIDE. 3435 
dorsal cup to the top of the interbrachials and interdistichals almost equal 
to the height of the compartments for the reception of the arms. Dorsal 
cup subturbinate, massive, broadly truncate at the lower end, and the 
bottom part deeply excavated, the sides straight or a little concave ; 
surface of the plates flat and without ornamentation; the suture lines 
obscure. 
Basals sinall, at the bottom of a deep, funnel-shaped concavity, and 
forming with the inflected lower part of the radials, at the inner floor, 
a rather large cone with a pentapetalous axial canal of moderate size. 
Radials very large, much longer than wide, forming a broad, slightly 
spreading cup, which extends out laterally far beyond the sides of the 
column. First costals quadrangular; their length and breadth equal; the 
greatest width at the base; the lower and lateral faces convex. Second 
costals smaller than the first, generally pentangular, occasionally the upper 
angle slightly truncated by the interdistichal. First distichals almost as 
large as the axillary costals; the second but one third the size of the first. 
First palmars very short and trigonal. First interbrachial almost as large 
as the radials; length to width as 5 to 3; its greatest width at the inter- 
costal suture line, whence it rapidly tapers to both ends; all sides concave. 
The two plates of the second row either separated from the first, or lightly 
touching its upper angle, and both together about two thirds the size of the 
first; they rise above the arm bases in form of a square projection. The 
interdistichal is of a similar form as the two upper interbrachials, but one third 
smaller, Ventral disk, deprived of its appendages, pyramidal, the neck-like 
upper part proportionally long, widening at the top, the compartments sur- 
rounding it deep. These are constructed of the keel-like partitions ascend- 
ing from the back of the plates of the first row, and the wing-like extensions 
of the upper row, which meet each other at the middle of the third row, 
resting with their inner edges against the protruding surfaces of the plates 
constituting the second and third rows. The form of the plates of the first 
ring, as viewed from the inner cavity, is similar to that of the first inter- 
brachials; they are as large, and also attenuate at both ends. ‘The plates 
of the second ring, which are quite massive and elongate, form a reversed 
funnel with its long tube pointing upwards; those of the third ring are 
short and narrow, and those of the fourth rather long and wider above than 
below. The canal within the neck widens toward the extremity, and the 
top is closed by a short pyramid of small, irregular pieces surrounding the 
