214 DISCOVERY REPORTS 



The basal cup has strongly rounded sides. The radials are widely separated from one 

 another. The arms of only two rays are complete ; they are of five brachials. The radianal 

 plate is in broad contact with the right posterior radial which it makes asymmetrical; 

 it is in contact with the proximal half of the left posterior radial. It overrides the oral ; 

 no naked perisome is to be seen in this interradius. In other interradii the orals may be 

 separated from the basals by a narrow strip of perisome. 



The edges of the orals become free opposite the costals, beyond which the plates 

 narrow as they turn in over the disk. 



There are side-plates along the ambulacra of the arms. 



5. Length of crown 1-9 mm. ; length of column 9 mm. 



The column is generally similar to that of previous stages. There are 43 columnals and 

 a round terminal plate which appears to be simple. The first seven columnals are short 

 and discoidal and become progressively more narrow from the first to the seventh. The 

 tenth to about the twentieth are about as long as broad, the remainder broader than long. 



The crown is smaller than in the previous stage and the basal cup is not so strongly 

 rounded. Some of the radials are widely separated, others less so, and one pair, the 

 right posterior and the right anterior, are in contact. The centre of the radianal plate is 

 to the right of the mid-line of the posterior interradius ; it is in broad contact with the 

 right posterior radial which it makes asymmetrical. It is in less complete contact with 

 the left posterior radial. 



None of the orals is separated from the more proximal ossicles of its interradius by 

 naked perisome. They are shaped as in the previous stage. 



The arms are of about six brachials. 



6. Length of crown 2 mm. (Fig. 23 d) ; length of column 9 mm. 



The stem is similar to that of the previous stage. There are 42 columnals and a large, 

 rather thin and slightly lobed, terminal plate which does appear to be made up of more 

 than one element. 



The sides of the basal cup are strongly rounded ; its height is about half its distal 

 diameter. The radials, except for the right and left posterior, are nearly or quite in 

 lateral contact. By their lateral growth they have pushed the orals out of contact with 

 the basals ; where they are not quite in contact small naked areas of perisome separate 

 them from one another. The right and left posterior radials are separated by the radianal 

 plate which lies in broad contact with the former and in contact with the proximal third 

 of the latter. It causes the right posterior radial to be asymmetrical and the longitudinal 

 axis of its ray lies far to the right of the suture between the basals on which it rests. The 

 radianal plate rests on the oral. 



The lateral edges of the orals become free opposite the end of the costals ; beyond that 

 point they narrow and bend in over the disk. They are of the usual coarse texture, deeply 

 pitted proximally with some of the pits carrying glandular sacs. 



The left posterior ray is broken off" at the costal. The arms of the other rays are of 

 about eight brachials. There are a few small sacculi of the same appearance as the 

 glandular sacs. The arm ambulacra are lined by large side-plates. 



