PENTACRINOID LARVAE 205 



edges of the orals are still more strongly everted than in the previous stages ; the radials 

 are considerably, the costals and axillaries very much, larger. The axillary is as large as 

 the costal and carries two very small first brachials. 



The radianal causes the posterior basal and the right posterior radial to be asym- 

 metrical. The suture between the posterior and the right posterior basal plates is out 

 of fine with, to the left of, that between the corresponding oral plates; the axis of the 

 ray coincides with the latter. 



6. Length of crown 1-3 mm. ; length of column 67 mm. 



The column is of 33 segments. The first is very short and closely in contact with the 

 basal cup. The next five are short and discoidal and become progressively and gradually 

 smaller: that is, the second is shghtly longer and wider than the third, and so on. The 

 remaining columnals are similar to those of the stages already described : all but two or 

 three following the discoidal proximal segments and three or four near the terminal 

 plate are longer than broad, somewhat barrel-shaped, each with a narrow projecting 

 girdle ; the articular faces are broadly oval and the long axes of the two faces of each 

 columnal are at right angles to one another. The terminal plate is simple. 



The base of the basal cup is a little wider than the topmost columnal. Its distal 

 diameter is nearly twice its length ; its sides are nearly straight. 



The proximal portions of the lateral edges of the orals are widely separated by the 

 well-developed radials, costals and axillaries against which they are turned up; the 

 distal portions are in contact with one another. The radials are five-sided, about as long 

 as broad; they do not meet one another. The posterior basal and the right posterior 

 radial are made asymmetrical by the radianal ; the axis of the right posterior ray is not 

 in line with, but considerably to the right of, the suture between the posterior and right 

 posterior basals. The radianal appears to override the posterior oral. 



The costals and axillaries are strongly developed ; the latter reach as high as the apex 

 of the oral dome and each carries a pair of first brachials, and some a pair of second 

 brachials, which reach farther. 



This is the first stage in which the radial structures reach beyond the orals. 

 7. The crown is damaged, about 1-3 mm. long; length of column 7 mm. 

 The stem is of 26 columnals and a small thick terminal plate. The first five columnals 

 are short; the first and second are wider than the third to fifth. The remaining 

 columnals, except for two or three following the short proximal columnals and three or 

 four before the terminal plate, are longer than broad, the longest being one and a half 

 times as long as broad. In other ways they resemble those of the stages already 

 described. 



The basals and radials together form a straight-sided cup (as in the next stage, see 

 Fig. 21 e). The radials are pentagons with rounded angles; they do not meet. The right 

 posterior radial is made asymmetrical by the radianal which rests closely against it, and 

 the ray it bears lies to the right of the line of the suture between the posterior and right 

 posterior basals. The radianal is nearly in contact with the left posterior radial; it rests 

 on the posterior oral. 



