PENTACRINOID LARVAE 215 



7. Length of crown 2-2 mm. ; length of column 10 mm. 



There are 45 columnals and a large faintly lobate terminal plate which is single. The 

 first eight columnals are short and discoidal, of roughly equal length but gradually 

 decreasing in diameter from the first to the sixth. The remainder of the column re- 

 sembles those of previously described stages. 



The radials are widely separated. The radianal is in contact with the right posterior 

 but not the left posterior radial. Its proximal half lies on the naked perisome which 

 separates the posterior basal from the oral ; its distal half lies on the oral. The orals of 

 the other interradii are separated from their basals by very narrow strips of perisome. 

 They are shaped as in previous stages and are richly supplied with glandular sacs : there 

 are as many as eight on one plate. 



Three of the rays have arms of eight brachials. The costals and axillaries of the right 

 posterior ray are smaller than those of others and its arms are of no more than three or 

 four brachials; the right anterior ray has equally short arms but they appear to be 

 broken, not undeveloped. 



The right posterior radial is made asymmetrical by the radianal, and the whole of the 

 ray, but for a corner of the radial itself, lies to the right of the line of the suture between 

 the basals upon which it rests. 



There are a few irregularly placed sacculi, of a similar appearance to the glandular 

 sacs, along the arms, and strong side-plates along the ambulacra. 



8. Length of crown 2-4 mm. ; the column is incomplete. 



Only 13 columnals remain. The first five are short and discoidal but longer than those 

 of previous stages. The sixth is about half as long as wide, the remainder about as long 

 as wide ; they are encircled by a narrow projecting girdle which is in the proximal half 

 of the sixth columnal but median in all the others. 



The crown is very similar to that of the previous stage except that : the radianal plate 

 lies entirely to the right of the mid-line of the posterior interradius ; all the arms are of 

 equal size, of about six brachials ; the basals and one of the radials — as well as the orals — 

 carry many glandular sacs in pits. 



9. Length of crown 3 mm. (Fig. 24 a); the column is incomplete. 



Only 29 columnals remain. The first is short and closely associated with the basal 

 cup. The second to fifth are short and discoidal. The sixth is discoidal but longer. The 

 seventh is about half as long as broad. The eighth to near the twentieth are as long as 

 broad, the remainder slightly broader than long. 



The crown is similar to, though larger than, those of the two previous stages. Each 

 of the basal plates is swollen so that the sutures between them run along depressions. 

 The distal half of the radianal plate lies, not on the oral, but on a lobe of tissue at a higher 

 level than, and overlapping the proximal edge of, the oral plate. I assume it to be the 

 beginnings of the anal tube. 



As in the previous stage from the same station (St. 175) there are glandular sacs on 

 other ossicles than the orals. 



The arms are of seven or more brachials. 



