The Circular Chinese Hat, Calyptraea centralis (Conrad, 1841), is a close relative of the more commonly found Slipper Snails. The half-inch species is a gastropod, albeit one with a cap-shaped, circular shell that could easily be mistaken for a little white clam valve. The shell "aperture," on the bottom is represented by a sinuous ("sigmoid"), flaring shelf inside shell. The shell color is invariably white.
![The Circular Chinese Hat, Calyptraea centralis, from Sanibel Island. Photo by José H. Leal.](https://static.wixstatic.com/media/7f077a_1eae28237fbe4ca691010a44e824bb61~mv2_d_2940_2658_s_4_2.jpg/v1/fill/w_147,h_133,al_c,q_80,usm_0.66_1.00_0.01,blur_2,enc_auto/7f077a_1eae28237fbe4ca691010a44e824bb61~mv2_d_2940_2658_s_4_2.jpg)
The Circular Chinese Hat, Calyptraea centralis, from Sanibel Island. Photo by José H. Leal.