OF WESTERN SIND. 153 



The ambulacral petals are long, extending nearly to the ambitus, distinctly petaloid 

 in outline, expanding in the middle portion, and contracting slightly towards the outer 

 extremity. The posterior pair are the longest and broadest, and the odd anterior 

 ambulacrum is the shortest and narrowest. The greatest breadth of the postero- 

 lateral petal is about t^q-o-o of the length of the test, being 8-50 millim. in a test 

 58 millim. long. The poriferous zones in the postero-lateral and in the odd anterior 

 petals are subequal, the companion zones in each petal not varying in length from each 

 other by more than one or two pairs of pores. In the antero-lateral petals, however, 

 the posterior zone is longer than the anterior zone of the same petal by ten or more 

 pairs of pores. The posterior zone of the antero-lateral petals is more curved than the 

 companion zone, forming a rather wide sweep into the lateral interradia, the convexity 

 directed backwards. The relative curvature of the zones in the other petals is about 

 equal; and the general direction of the petals from the apex outwards is almost 

 straight. The poriferous zones are comparatively narrow, varying very little through- 

 out their length after attaining the normal width at a short distance from the apex, 

 and their width decreasing very slightly at the outer extremity. The inner pores are 

 round, the outer pyrifortn or comma-shaped, and they are united by a deep, well- 

 defined groove. The divisional costee are narrow, and were originally ornamented with 

 a single row of five or six small granules, of which, however, nearly all traces are now 

 obliterated, except in one or two very rare instances. The position of the pairs of 

 pores and of the costse is slightly oblique, the line of direction from the inner to the 

 outer pore being slightly adoralwards. The width of the poriferous zone at its widest 

 part is 1-50 millim. ; and the width of the interporiferous area at the broadest part of 

 the postero-lateral petal is 5"5 millim. The extra-petalous continuation of the pori- 

 ferous zone is indiscernible until well on the actinal surface, where its course is indi- 

 cated by a very shallow depression, which becomes more distinct as it approaches the 

 peristome. The interporiferous area within the petals is slightly tumid, and its orna- 

 mentation is similar to that of the interradia, consisting of numerous small primary 

 tubercles situated in rather deep scrobicules, so closely placed that the interspaces, 

 which are always less in breadth than the diameter of a scrobicule, have usually only 

 the two rows of miliary granules upon them which form the boundary of two adjacent 

 scrobicules, one round each. The tubercles are the most numerous and crowded at the 

 ambitus and just beneath, and the most widely spaced in the neighbourhood of the 

 peristome. They are, perhaps, a shade larger on the actinal surface, but the difference 

 is very slight. 



The peristome is slightly exceutric in front ; it is large, subpentagonal, deeply 

 impressed, and with high vertical walls. The ambulacral areas become very contracted 

 as they approach the peristome, and are slightly sunken, forming shallow troughs, 

 especially in the three anterior ambulacra, which emphasize the very slightly swollen, 

 incipient bourrelets of the anterior interradia. This slight development of the bour- 

 relet is wanting in the three posterior interradia ; and the margin of the peristome 

 bounded by the odd posterior interradium has the test rather less tumid, and is instead 

 more inclined towards the mouth, than the other parts surrounding the aperture. 



