OF WESTERN SIND. 203 



two lateral petals on either side of the test usually forming two more or less definite 

 arcs which touch at their convexity at the apical disk. Poriferous zones equal, very 

 wide ; pores equal or subequal. The anterior zone of the anterior petals and posterior 

 zone of the posterior petals having some pores atrophied at the apical extremity. The 

 odd anterior ambulacrum is placed in a shallow sulcus ; its poriferous zones are composed 

 of simple minute pairs of pores, widely spaced. 



Peristome bilabiate, excentric in front. 



Periproct oval, on the posterior extremity. 



Two fascioles : a peripetalous one, more or less sinuous, which surrounds the petals 

 and approaches the anterior margin ; a subanal fasciole, which is complete. 



Tubercles perforate and crenulate, small on the upper surface ; larger and more 

 widely spaced below the ambitus, especially in the anterior region and on the actinal 

 surface. 



1. Beissopsis sufflatus, Dimcan & Sladen. Plate XXXV, Figs. 17-24. 



Test of medium size. Marginal contour elongate, elliptical, greatest breadth across 

 the middle, converging equally anteriorly and posteriorly, narrow in front, with the anterior 

 margin widely and rather deeply indented by the anterior groove, truncate posteriorly. 

 The greatest breadth is rather less than three fourths of the length, or in the proportion 

 of 0"73 : 1. The dorsal surface is subdepressed, very tumid in the interradia, and the 

 margins are thick and tumid. When seen in longitudinal profile the dorsal surface 

 has a remarkable appearance, presenting three convex undulations, which represent the 

 outline of the interradia — the median undulation formed by the lateral interradia being 

 rather higher than the anterior undulation, and the posterior undulation being a little 

 higher than the lateral (median) undulation. The greatest height of the test conse- 

 quently lies near the posterior extremity of the test, and when measured from the 

 culminating point of the actinal plastron to the highest part of the odd posterior 

 interradial convexity, is less than half the length, or in the proportion of 0"45 : 1. 

 The actinal surface is rather flatly convex, being well rounded to the margin, and is 

 characterized by the presence of a sharp angular keel or ridge, which extends along 

 the median longitudinal line of the test from the peristome to the culminating point 

 of the plastron, the height increasing as it approaches this point; the test then 

 sharply diminishes with a precipitous slope, which terminates "abruptly at the posterior 

 truncation. 



Apical disk excentric in front. The posterior pair of generative pores rather 

 wider apart than the anterior pair ; and the posterior pair of ocular plates separated by 

 the prolongation of the central madreporiform body. The groove of the odd anterior 

 ambulacrum is wide but very shallow, and appears to mount the convexity of the test 

 which intervenes between the apical disk and the anterior margin ; it is deepest just 

 above the ambitus, where the indentation of the anterior margin is well defined, but its 

 continuation on the actinal surface towards the peristome becomes very faiat. The 

 poriferous zones are straight and rather near together, the pores being very minute and 



