OF WESTERN SIND. 255 



actinal margin of the radial plate is nearly equal to that from the margin to the angle 

 of a basal plate. The ornamentation of the plates consists, besides the miliaries 

 already noticed, of others which are on either side of the tubercle on the basals, and a 

 group on the radial plates. Eidges pass from the great tubercle outwards and down- 

 wards, cross the basal plate, and reach the radial and pursue the same direction. 



3. The width of the ambulacra is not much more than one half of that of the 

 interradia at the ambitus, and this is very characteristic. The tubercles reach up nearly 

 to the radial (optic) plate. 



4. The pores are large and circular, and the pairs very distinct ; the poriferous 

 zones form a wide angle at the radial plate. 



5. In large specimens there are 26 tubercles on the interporiferous area, with 

 three pairs of pores to the 13 large tubercles on either side of the median line; the 

 intrusion of the pores into the scrobicular circle is common to this and other species 

 (Fig. 10). The lower pair of pores of the triplet is nearer the median line than the 

 others ; and in well-preserved specimens the pairs are separated by a surface on which 

 there is a row of three small miliaries ; the pores are non-conjugate. The arrange- 

 ment of the ambulacral plates is as in all Ccelopleuri. The large tubercle has a sutural 

 line which passes on to and up it close to the mamelon from the upper pair of pores ; 

 it then suddenly turns abactinally, and reaches the abactinal edge of the plate. A 

 corresponding line passes from the middle pair on to the tubercle ; it does not touch 

 the other, however, but curves actinally to reach the actinal edge of the plate. Hence 

 a space exists between these two sutural lines, and comprehends the space between the 

 middle pair and the upper pair of pores, the mamelon on the top of the tubercle, 

 and all the plate towards the median line. There are thus three plates to each tubercle- 

 bearing plate — one abactinal, small ; one actinal, nearly of the same size and shape : and 

 one between these, narrow at the top of the tubercle but comprehending the mass of 

 the plate. The small plates are demi-plates and do not reach the median line, but the 

 middle plate is great and does so. The third pair of pores has its adoral pore on the 

 actinal line of suture of the lower small plate. (Fig. 12, and see Fig. 7 : these 

 drawings are semi-diagrams.) The imperfect union of the sutures shows that plates 

 1 and 3 are intercalated on the large plate 2 of the triple combination. Near the 

 peristome the pairs of pores become small and more oblique. 



The peristomial cuts are visible and small : a tag passes abactinally close to the 

 poriferous zone, which is long and narrow, and is crossed actinally by ridges and 

 grooves. 



6. The median line of the ambulacrum, narrow in the extreme from the size of the 

 bases of the bosses, has a row of miliaries on it, but actinally at the angles of the 

 sutures in the median line there are fossettes, which vary in size and depth, and may 

 not be present. 



7. The interradia, bare abactinally to the sixth plate from the generative plate, 

 are slightjy concave there on the median line, and this part is bounded laterally by a 

 rather broad edge which carries a vertical row of secondaries separated by miliaries, 

 which also are seen beyond and near the pores of the ambulacra. At about the fifth 



2 u 



