OF WESTERN SIND. 333 



zones of the antero-lateral petals and the posterior zones of the postero-lateral petals 

 being shorter than the companion zone of the same petal. The breadth of the poriferous 

 zone, excepting the narrow apical extremity, varies only slightly throughout the major 

 portion of its length, the decrease towards the outer extremity being slight. At the 

 widest part of the petal, the width of the poriferous zone is rather less than one third 

 of the width of the interporiferous area, the actual breadth of the poriferous zone being 

 only 1"125 millim. in an example 55 millim. in length, but is often less. The inner 

 pores of a zone are round, and the outer ones slightly elongate or pyriform, the pair 

 being united by a well-developed channel ; and the posture of the pairs of pores is very 

 oblique in relation to the zone. The divisional costa between each pair is ornamented 

 with a single line of small miliary granules. Near the extremity of the anterior zone 

 of the antero-lateral petals the zone is distinctly and rather suddenly incurved (concavity 

 forwards), which gives a slightly sigmoid character to the zone, especially in comparison 

 with the regularly arched and longer companion zone in the same petal. The extra- 

 petalous continuation of the poriferous zones is scarcely visible to superficial observation 

 until midway on the actinal surface, between the margin and the peristome ; although 

 in some favourable examples the course of the zones of the odd anterior petal are more 

 or less faintly defined throughout by slight channelling. When the poriferous zones 

 reach the neighbourhood of the peristome they are sensibly channelled, the pores are 

 distinct, and well-developed sublyriform phyllodes are produced. A regular internal 

 series of pores, one pore opposite alternate pores of the outer series with more or less 

 regularity, is present ; and a double series of pits (presumably for sphseridige) are situated 

 in the median radial line of the phyllode. The interporiferous areas may almost be 

 said to be flush with the test, although in some cases those within the petals of the 

 paired ambulacra are very faintly tumid. The ornamentation of the areas both within 

 and without the petals is similar to that of the interradial areas. 



The lateral interradial areas are the broadest, and their breadth is nearly equal to 

 the whole area included by the antero-lateral ambulacra, i. e. to the two anterior inter- 

 radia and the odd anterior ambulacrum combined. The anterior interradia are by far 

 the smallest. In the odd posterior interradium there is considerable tumidity abacti- 

 nally, over and conformable with the posterior rostration ; and there is also considerable 

 tumidity on this area on the actinal surface along the median line between the peristome 

 and the periproct, the swelling expanding and gradually dying out as it approaches the 

 latter aperture and the posterior margin of the test. There is considerable tumidity in 

 the posterior column of the postero-lateral interradia, which conspicuously aff'ects the 

 marginal contour, and constitutes one of the features that contributes largely to the 

 characteristic form of this species. The ornamentation of the interradial and inter- 

 poriferous areas is uniform and small, and consists of small primary tubercles, sunken 

 in rather deep, narrow scrobicules, the intermediate spaces being about equal to half 

 the diameter of the scrobicule, and having the surface covered with small, distinct, and 

 not particularly crowded miliary granules. On the abactinal surface, in well-preserved 

 specimens, a distinct ring of granules encircles each scrobicule ; there are thus two rings 

 of granules in each intermediate space between scrobicules, and a few extra at the angles 



