PENTACRINOID LARVAE 207 



attached to the basal cup. The second to fourth are wider and more robust than the 

 first and fifth and sixth ; the second is wider than the third and the third than the fourth. 

 None of the columnals has a median girdle. The terminal plate is large. 



The sides of the basi-radial cup are straight. All but the posterior radials are in 

 broad contact. The proximal corners of the posterior radials meet, cutting off^ the 

 radianal plate from contact with the basal for the first time ; the distal portions of the 

 posterior radials are separated by the radianal. Its centre lies to the right of the midline 

 of the posterior interradius and it is in contact with the costal of the right posterior ray 

 as well as with the two radials; its centre is in line with the articulation between the 

 radial and the costal. Both the posterior radials are made asymmetrical by the radianal, 

 the right far more so than the left, for its left distal corner is cut away to accommodate 

 the radianal. The radianal overlaps the posterior oral. 



The bases of the orals are in contact with the inner distal edges of the radials. They 

 are flat plates with slightly out-turned edges which bend in over the disk, where their 

 edges appear to meet, and are evenly rounded distally: they do not narrow to bar-like 

 projections. 



The costals and axillaries are considerably stouter than in the previous stage (No. 9). 

 The arms are of 12 or 13 brachials. There are no pinnules and I can see no sacculi or 

 side-plates along the arm ambulacra. 



11. Length of crown 3-5 mm.; length of column 11 mm. 



There are 36 columnals and a large lobed terminal plate. The first five columnals are 

 short and irregular. The first and second are as wide as the base of the basal cup, the 

 second a little longer than the first. The third and fourth are slightly, the fifth con- 

 siderably, narrower. The remainder of the stem is similar to those of Nos. 9 and 10. 

 None of the segments has a median girdle. 



The sides of the basi-radial cup are straight. All the radials are in broad contact 

 though that of the posterior radials is incomplete distally because of the radianal which 

 lies in contact with both of them and the costals they bear. It is a nearly circular plate 

 lying in the mid-line of the posterior interradius, its proximal edge opposite the 

 articulations between the radials and the costals, its centre opposite a point a third of 

 the way along the costals. Its contact is closer with the right than the left posterior ray. 

 It lies much nearer to the outside than the oral. 



The orals lie deep within the arms, their bases in contact with the inner distal edges 

 of the radials, their lateral edges underneath the edges of the arms on either side. They 

 bend in over the disk, gradually narrowing as they do so : their edges probably do not 

 meet over the disk. 



The costals, axillaries and brachials are considerably more robust than in No. 10. 

 The arms are of about 14 brachials; the ninth and tenth brachials of some arms bear 

 the beginnings of the first pinnules to be formed. I see no sacculi and no side plates 

 along the arm ambulacra. 



12. Length of crown 5-6 mm. (Fig. 22 d); length of column ca. 12 mm. 



There are 36 columnals and a large lobed terminal plate. The first columnal is short 



