PENTACRINOID LARVAE 209 



the former but not with the latter. It is a long narrow plate lying between the posterior 

 rays, just below the level of their edges. The oral plate can be seen deep within the arms 

 behind it (but not in such a way as to be shown in the figure). The proximal border of 

 the radianal plate is half-way along the costal, its distal border opposite the beginnings 

 of the first brachials. 



In two of the remaining interradii the arms are too closely pressed together for the 

 oral plate to be seen. In each of the other two the oral is visible, its base opposite the 

 middle of the axillary, i.e. for the first time out of contact with its radials, its distal portion 

 sloping steeply inwards. I can see no plates in the perisome separating it from the radials. 



The costals, axillaries and brachials are more massive than in the previous stage. The 

 lateral edges of the axillaries are parallel. The arms are of about 20 brachials; from the 

 ninth brachial onwards there are pinnules of up to eight segments. There are a few small 

 irregularly arranged sacculi on some arms. There appear to be small side-plates along 

 the arm ambulacra. 



13. Length of crown 5-4 mm. ; length of column 12 mm. 



The column is of 34 columnals and a large lobed terminal plate. It is very similar to 

 that of No. 12. The first columnal bears five slightly longer cirri, the longest as long as 

 the side of a basal plate. 



The crown is very similar to that of No. 12. The sides of the basi-radial cup are 

 straight in the proximal basal portion, bulge slightly outwards in the radial portion. 

 The right distal corner of the left posterior radial extends a little farther forward than 

 the contiguous corner of the right posterior radial — not nearly so much so as in No. 12 : 

 the radianal is far removed from it. The proximal edge of the radianal plate is opposite 

 a point half-way along the costal ; the proximal edges of the orals are opposite the distal 

 edges of the costals. There are a few sacculi and small side-plates along the arms. 



14. Length of crown 6-8 mm. (Fig. 22 e); length of column 13 mm. 



There are 35 columnals and a large lobed terminal plate. The first columnal is longer 

 and more massive than in the previous stages. It bears two whorls of cirri, a radial 

 whorl of five larger cirri arising from large sockets occupying nearly the entire length 

 of the segment, and an interradial whorl of five very small cirri arising from the 

 proximal half of the segment. The longest of the radial cirri consist of more than 12 

 segments and are longer than the basal plates. The second columnal is discoidal, of the 

 same diameter as, but shorter than, the first ; its proximal edge is not notched opposite 

 the cirri of the first. The third is shorter and narrower than the second and irregularly 

 discoidal. The fourth and fifth are still narrower but slightly longer. The remainder of 

 the column resembles that of the stages described above. 



The contiguous distal corners of the posterior radials are unequal as in Nos. 12 

 and 13. The radianal plate is more distant from them than in those younger specimens: 

 its proximal edge is opposite a point a third of the way along the axillary ; it extends to 

 a third of the way along the first brachial. It is smaller than in specimen 13. It rests on 

 the anal tube which ends opposite the distal half of the first brachial. The oral plate may 

 be seen deep behind the end of the anal tube. In other interradii it may be seen that the 



