OF WESTERN SIND. 79 



The marginal outline is ovoid, broadest centrally, broader in front than behind, 

 where the test diminishes in breadth rapidly. The anterior margin is well rounded, the 

 groove not reaching to the ambitus ; and on a line with the antero-lateral ambulacra 

 there is some marginal flattening. A side view of the test shows the tumid margin 

 sloping backwards more rapidly than forwards ; the highest point is far back ; thence 

 the test slopes backwards rapidly over a very flat broad keel to overhang the periproct, 

 and forwards more gradually but decidedly to the low tumid anterior margin. The 

 test stands on a smaller base than the margin ; and the height of the test diminishes 

 rapidly in front of the very eccentric-in-front peristome. Posteriorly and below is 

 the pointed plastron-end, and the test slopes rapidly upwards and backwards, and then 

 nearly upwards to the periproct. The outline of the test seen from behind is depressed 

 at the sides, pointed below, faintly rounded and keeled above. Anteriorly, the outline 

 indicates a rounded actinal surface, showing the opening of the peristome, a low tumid 

 margin, and a broad low ambulacral groove with a low keel on either side of it. 



The apical system is slightly behind the centre of the test, is small, and is situated 

 on a narrow transverse keel of the lateral interradia. The peristome is very eccentric 

 in front. The periproct is situated about three fourths of the distance from the pointed 

 end of the plastron to the summit of the test. 



The apical system is compact and small ; the madreporic body is small, and sepa- 

 rates the posterior ocular plates, but does not extend into the posterior interradial area ; 

 there are only two generative pores, and they are situated at the tops of truncated 

 cones separated at their bases by the granular surface of the madreporic. The cones 

 are at the extremities of a narrow transverse ridge. The right and left antero-lateral 

 generative plates are very small, and they are not perforated by pores ; and the postero- 

 lateral plates are the largest and are perforated. There is no posterior generative 

 plate. The ocular plates are well developed, and are placed in hollows, and intrude on 

 the generative-plate edges. 



The odd anterior ambulacrum is in a shallow groove, which widens and shallows 

 anteriorly until it is just lost at the ambitus; there is a keel on either side, which 

 diverges from its fellow, and which, well developed near the apical system, gradually 

 broadens and becomes lower anteriorly. The keels slope rather rapidly towards the 

 base of the groove; and the ambulacral. pairs of pores are situated partly on the base 

 and partly on the slope. They are few in number, are oblique, and the pores of each 

 pair are separated by a small tubercle. Beyond the fascicle the pairs become very 

 rare. 



The antero-lateral ambulacra, in shallow grooves, are small, form an angle of about 

 90°, are petaloid, very nearly closed, slightly sinuous, broadest in the outer half, and 

 fairly rounded close to the fasciole which closes them. The poriferous zones are large 

 and on difiierent levels, the anterior being on the slope of the test, caused by the keel 

 of the anterior odd ambulacrum, and the posterior nearly flat. The pores are conju- 

 gate, rather wide apart, elongate, and the inner are the smallest; near the ocular 

 end the pores of the anterior poriferous zone are smaller than those of the posterior 



m2 



