212 DISCOVERY REPORTS 



against the oral plates, and although they were not partly enclosed in their stereom it 

 seemed that they might easily become so as growth went on. 



Such sacs occur in all the older larvae to be described in this series. They are some- 

 times abundant and may occur in superficial pits in the surfaces of the basals, the radials, 

 the costals and the axillaries as well as in the orals. 



2. Length of crown i-6 mm. (Fig. 23 b); length of column 67 mm. 



The stem is of 36 columnals and similar to that of the previous stage. A larger num- 

 ber, about 12, of the distal columnals are shorter than broad and they are slightly wider 

 than the other columnals; they become progressively wider as they approach the ter- 

 minal plate. The terminal plate is simple, thick and slightly irregular. 



The radials are widely separated from one another. The rays are bigger than in No. i ; 

 the arms are of five brachials and extend well beyond the orals. The proximal edges of 

 each oral rest against the basal, the radials and the costals of its interradius. Opposite 

 the axillaries it narrows into a strap-like projection with slightly out-turned edges which 

 curves in over the disk. The projections of the five orals do not enter into close contact. 

 The orals are of very coarse texture. The surface of the proximal portion of each is 

 pitted and some of the pits carry glandular sacs of diverse sizes. One or two of the 

 radials and costals carry similar sacs. There is a single sacculus on one of the arms which 

 has exactly the same appearance as the glandular sacs. 



The radianal plate occupies an unusual position : its centre lies to the left, not right, 

 of the mid-line of the posterior interradius and it lies close against, and causes asym- 

 metry in, the left, not the right, posterior radial. The corner of the right posterior radial 

 is just in contact with it. The distal half of the radianal rests upon the posterior oral. 



3. Length of crown 1-9 mm. (Fig. 23 c); length of column 8 mm. 



The stem is of 39 columnals and a terminal plate which is large and lobed but does 

 not appear to be composed of more than one element. The column is generally similar 

 to that of the younger stages but there are slight diff^erences : the discoidal proximal seg- 

 ments, of which there are nine, are even shorter, whereas the majority of the middle 

 segments are slightly longer, being a little longer than broad. 



The radials are widely separated. Three of the rays are stronger than in the previous 

 stage, the arms of about six brachials. The anterior and the left anterior rays are small, 

 bearing only the first brachials; they are shorter than the orals. The lateral edges of the 

 orals become free opposite the costals, beyond which the plates rapidly narrow to in- 

 wardly curved strap-like ends. Some of the orals are in contact with the basal plates of 

 their interradius, others separated from it by a very narrow strip of perisome. A wide 

 area of perisome separates the posterior oral from its basal. On it lies the radianal plate 

 with its distal end overlapping the oral. 



The centre of the radianal plate lies to the right of the mid-line of the posterior inter- 

 radius but it is not in contact with the right posterior radial, which, nevertheless, is 

 strongly asymmetrical. The axis of its ray lies far to the right of the suture between the 

 posterior and right posterior basals. The proximal left-hand corner of the radianal 

 touches the left posterior radial. 



Strong side-plates are developed along the ambulacra of the arms. 



