146 



r 



Journal of the Asiatic Society of Bengal, 



[March, 1907. 



ambulacral plate, external to the internal fasciole. Internal to 

 the widest ^ part the pores of the anterior zone are partially obli- 

 terate, the internal pore disappearing before the external. Be- 

 -tween the internal fasciole and the apical system the pairs of pores 

 are exceedingly minute, but visible with a ieus. 



Owing to the anterior position of the apical system the petals 

 of the postero-lateral ambulacra cease at 13 mm. distance from the 

 posterior ^ margin of the test ; the poriferous zones form an elon- 

 gated ellipse, and not a wide angle with one another as in 



B. australasim 

 minute. 



sternum and 



ero 



the internal fasciole the pores are yqty 



ambulacra with the adjacent parts of the 

 ateral interambulacra form wide, bare, 



triangul 



smooth 



margins especially anteriorly, tubercular centrally ; the labrum 

 IS very narrow and elongated measuring 7-5 mm. in length. 



The 6th— 15th plates of the postero-lateral ambulacra are 

 partially enclosed m the subanal fasciole ; and of these the 7th— 

 14th inclusive have the pores within the fasciole modified. 



The peristomial membrane is covered with plates diminishing 

 m size from the attached to the free margin. . 



The periproct, situated in the upper part of the posterior 

 truncation,_ is sunken and funnel-shaped and overarched by the 

 posterior mterambulacrum. The anus is situated in the upper 

 part of the penproctal membrane which is covered with several 

 rows of plates of which the lowest are by far the largest 



Ihe subanal fasciole is wide and triangular, very broad 

 above, narrowing inferiorly. The peripetalous fasciole is very 

 narrow and extends but a short distance behind the extremity of 

 the postero-lateral ambulac. a ; anteriorly it can only be traced to 

 the margms of the odd ambulacrum. The internal flsciole is cone- 



rounded 



is widest and 



most distinct pos- 

 terioriy, nairowest anteriorly, where it sends off a branch to the 

 margin of the odd ambulacrum, and ends by bending towards 

 the odd ambulacrum across which it can very nearly be traced. 

 On the entire abactmal surface there are but three perforate, 



iXl^K 7 ' ^'^^ f ""^"'^ scrobicules, in one anterolateral 



interambulacru a a single one, in the other antero-lateral inter- 

 ambulacrum tw. placed one below the other, the one furthest from 



ZnJr^ aT^ ''*^^*^^ f""'^ ^ *^« peripetalous fasciole, the 

 second and large^ one adjacent to the ambulacral petal. All 



™ ""T-^ t^fcercles are situated on plates of the posterior 



fasciSe « wrT^'"" f ?^ °^^ ambulacrum within the internal 



the msLv^^nfThl Ji l^^^ ""^ ^"'"^'^^^ tubercles extends along 

 :n!;i?.^!!f.-.^f *^" ""^^ ambulacrum to the ambitus, and a few 



near 



large primary 



surface of flio i^ . • -^ tubercles. The remainder of the upper 

 surface of the test is covered with small tubercles with nume^us 



