FOSSILS FROM PERIM ISLAND. 411 



section fheir outline is oval with a diameter of g^g-g- to -g-gVir- ^^ some 

 places the radiating calcigerous tubes are ciit across, and take the form 

 of numerous dots in the field, like the ends of ivory tubes, and under a 

 low power have a moniliform or beaded appearance. The diameter of 

 the concentric circles is about -i^^ inch, there being from five to eight 

 rings of cells in each circle. 



I 



