OF WESTERN SIND. 175 



surface is very striking, passing with a well-rounded curve over the anterior extremity, 

 which is continued on to the actinal surface ; the posterior curve is more rapid, and 

 terminates above the periproct, forming a rather prominent roof over that aperture. 

 Seen in transverse profile the subcylindrical form is evident, the convexity of all regions 

 being remarkable. The actinal surface is almost as convex as the abactinal. The 

 apical disk is very excentric in front, its distance from the anterior extremity being 

 five sixteenths of the length of the test. There are four well-developed generative 

 pores, and the anterior are much closer together than the posterior pair. The ocular 

 foramina are comparatively large and distant from the disk, as defined by the gene- 

 rative pores. 



The ambulacra are petaloid and unequal. The odd anterior is the shortest, and 

 the posterior pair are the longest. All are lanceolate and tapering towards the apex, 

 and more or less convergent at the outer extremity, the odd anterior petal being the 

 least so. In the odd anterior ambulacrum the poriferous zones are equal, each having 

 eleven pairs of pores. The distance of the pores apart in each pair increases from the 

 apex up to the ninth pair and then begins to diminish, this giving the tendency to 

 closure in the petal's outline. All the pores are round, and those of a pair are united 

 by a well-defined conjugating furrow. The antero-lateral petals are equal in breadth 

 to the odd anterior petal or perhaps the slightest shade wider. The poriferous zones 

 are unequal, the anterior zone being shorter than the posterior ; the number of pairs of 

 pores in each is nine and thirteen respectively ; and the posterior zone forms a sweeping 

 well-rounded curve, convexity backwards. The posterior petals are a shade wider than 

 the anterior pair, and are considerably longer. The poriferous zones are unequal, the 

 anterior being the longest. The number of pairs in each zone is seventeen in the 

 anterior and fourteen or fifteen in the posterior. All the petals terminate at the 

 commencement of the rounding of the margin, and are consequently entirely confined 

 to the dorsal area. 



The peristome is very large and subelliptical in shape, placed transversely, the 

 lateral extremities being acutely angular. The breadth is 4 millim., and the length 

 2 millim. It is excentric in front, but much less so than the apical disk. There is 

 no peristomial wall or lip, and no traces of phyllodes or bourrelets have yet been 

 developed. 



The periproct is large and transversely oval ; it is inframarginal, with the plane of 

 the orifice nearly at an angle of 45° to the plane of the actinal surface, its position 

 being in the rounding between the ambitus and true actinal area. The posterior 

 interradium forms a prominent roof over the upper margin of the opening. 



Memarks. Owing to the juvenile character of the tests under notice, we have 

 abstained from assigning any name to them until a further supply of material can be 

 studied. From the fact that we are unable to associate them with the young of any 

 of the forms described in the preceding pages, it would seem to be probable that they 

 may belong to a distinct species. 



Dimensions. Length of the test 16 millim., breadth 12 mUlim., height 9*5 millim. 



2a2 



