OF WESTERN SIND. 13 



1. EcHiNANTHUS PUMILUS, sp. nov. Plates II & III. 



General form depressed, longer than broad, convex above; sides high, rounded 

 and tumid ; actinal surface slightly concave towards the mouth. Marginal contour 

 rather widely oval, broadest posteriorly, slightly truncate at the posterior extremity, 

 and faintly incised by the shallow infraperiproctal groove. The longitudinal profile 

 shows the apical summit excentric in front, the posterior slope very slight indeed, the 

 anterior one rather more rapid and rounded, and the whole dorsal area comparatively 

 flat, in consequence of the uniformly high, thick margin or sides, equally rounded 

 above and below. The transverse profile a regular curve, of slight elevation, very 

 faintly conoid over the apical summit. Posterior extremity slightly truncate, almost 

 vertical. Periproct elongate, oval, vertical, situated at the extreme top of the 

 extremity, the margins above and laterally being slightly carinate, whilst an extremely 

 faint groove is developed below, which dies out as it passes over the margin onto the 

 actinal surface. 



The apical systeih corresponds with the apical summit of the test, is excentric in 

 front, the distance from the centre of the system to the anterior margin being about 

 40 per cent, of the length. The generative pores, four in number, are large ; the 

 anterior pair closer than the posterior, the large madreporiform body, which occupies 

 the space between, being covered with miliaries. The ocular plates are large, although 

 their pores are very small. The anterior ocular plate fits in between the anterior 

 generative plates, and also the ocular plates of the antero-lateral ambulacra between 

 the anterior and posterior genital plates. The posterior ocular plates do not come so 

 far within the posterior generative pair, and are themselves separated by the intrusion 

 of the madreporic body. 



The ambulacra are narrow, rather short, and nearly equal, the posterior being 

 slightly longest. All are subpetaloid and open externally, the posterior pair ending a 

 little nearer the margin than halfway from the apex, the other ambulacra approaching 

 the ambitus more closely. The anterior ambulacrum is a shade narrower than the 

 others; and the poriferous zones do not approximate as they approach the ambitus, 

 so as to form a petaloid interporiferous area, the breadth of which in this ambulacrum 

 is as great at the distal extremity as at the middle of the petal. The anterior pair 

 of ambulacra form an angle of 136° with one another, and the posterior pair an angle 

 of 57°, this latter being the index of the odd posterior interambulacrum. 



The poriferous zones are narrow and of uniform breadth tliroughout, excepting 

 the normal diminution of size at the extremity on approaching the apex. The zones 

 are slightly sunken, and the interporiferous areas slightly raised or flush with the test; 

 and the zones of the odd anterior ambulacrum are a little irregular in their direction. 

 The breadth of the poriferous zone is rather less than one half of the breadth of the 

 interporiferous area. The pores are equal, round, and conjugate, the grooves being 

 oblique and very distinct ; the keel between with a row of granules. There are about 

 26 to 28 pairs of pores in each zone of the anterior and antero-lateral ambulacra, and 

 32 in the posterior. A single pore only of each zone is continued from the termi- 

 nation of the petals and passes over the ambitus, i. e. one pore to a plate, situated in a 



