C AL YPTOCRINID^ . 343 



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 small, 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. 

 Eadials 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. Yentral 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 



