OF WESTEEN SIND. 227 



about three eighths of the length of the test. All structure has entirely disappeared, 

 the test being very thin, and this portion is unfortunately quite worn away. 



The groove of the odd anterior ambulacrum is not defined until some distance 

 away from the apical disk ; it then gradually presents itself as a wide, shallow, depressed 

 tract, which, faintly, but distinctly, indents the anterior extremity, dying out just 

 below the ambitus, and not being continued on the actinal surface ; its floor appears to 

 have been naked, or with very minute granulation. The anterior pair of petals are 

 short, very widely divergent, of nearly uniform breadth throughout, and their course is 

 conspicuously curved, forming a distinct arc with the convexity backwards ; each petal 

 is situated in a shallow subtriangular depression, or concavity of the test, which extends 

 over more than half of the anterior interradium, thinning out gradually towards the 

 front and the margin, and the deepest part being defined by the curved line of the 

 petal. The poriferous zones are broad, nearly uniform in breadth throughout, and run 

 parallel with one another ; the pores are equal, transversely oval, wide apart, and united 

 by an indistinct conjugating furrow; the divisional septa, which are comparatively 

 broad, bore a few minute miliary granules in transverse line. The interporifeous area 

 is of uniform breadth throughout, and is narrower than the distance of the pores apart 

 in the poriferous zone. The posterior petals are longer than the anterior pair, are 

 straight in their course from the apex towards the margin, and subtend an angle of 

 about 42° ; they are of almost uniform breadth throughout, which is equal to that of 

 the anterior pair of petals; the poriferous zones, which are of uniform breadth 

 throughout, run parallel to one another, and their structure is similar, and equal in 

 all respects, to that of the anterior pair of petals. The posterior petals are situated in 

 shallow depressions of the test, which extend and die out on the lateral interradia, and 

 are perhaps somewhat less definite than those in which the anterior pair of petals are 

 placed. 



The anterior interradial areas appear tumid, or even with a tendency to become 

 subcarinate in their anterior zone which intervenes between the odd anterior groove 

 and the concavity of the test in which the antero-lateral petal is placed. The odd 

 posterior interradium is decidedly tumid, forming a low, widely expanded subcarinate 

 prominence along the median line, which slopes down to the depressed areas of the 

 postero-lateral petals, and in the posterior portion down to the margin. 



The peristome is rather small, bilabiate, with the posterior lip tumid, and its 

 position is very excentric anteriorly. 



The periproct is situate at the summit of the narrow posterior truncation, is com- 

 paratively large, and vertically subelliptical. 



The actinal plastron develops a low angular carination along the median line, which 

 reaches a culminating point at about two thirds of the distance from the peristome to 

 the posterior extremity, and is thence faintly continued along this secondary or pseudo- 

 subanal plastron, dying out entirely, however, at the rounding which takes place at the 

 inferior margin of the posterior truncation. The secondary plastron is remarkable, and 

 wholly actinal in position ; on either side are included six or more pairs of ambulacral 

 pores, from which may be inferred the former presence of a subanal fasciole, although 



