striated

They are spheric or ovoid, yellow in color, and have a thick, radially striated shell (Fig. 101).

The rock was singularly striated, the scratches arranged concentrically and in helicoidal curves.

The male has very large horns, with three rounded angles at the base, flattened in front, and striated transversely.

Shell striated and more or less ridged, but the name cristata refers to the plume-like appearance of its breathing apparatus.

The inner one is the zona radiata with a typical radiately striated structure.