The Echinoid Directory

Phyllodes and bourrelets

In cassiduloids, the structure of the test surrounding the peristome is particularly important taxonomically. The ambulacra here are typically enlarged and pores become more crowded and give rise to specialised feeding tube-feet. The pores may be single or double and may be arranged in a single irregular line, or as two distinct columns, or with an outer column and a scattering of internal pores as above. These enlarged areas of pores are termed phyllodes. The two largest pores closest to the peristome house sensory tube-feet and are generally a little larger than the others. These are the buccal pores (bp). The interambulacral zones adjacent to the peristome may be undifferentiated, or may be enlarged and swollen, forming distinct mounds or peg-like projections. These are the bourrelets and their lateral and adoral walls are covered in fine spines that help manipulate food particles into the mouth.