Periphylla, [311], [314], [322];

P. regina, [322]

Periphyllidae, [310], [322]

Periproct, of Echinus esculentus, [504], [507], [512], [513], [534];

of Endocyclica, [530], [534], [538];

of Cidaridae, [530], [533], [534];

of Arbaciidae, [530];

of Echinothuriidae, [535];

development of, in young Echinoid, [613]

Peripylaea (= Spumellaria), [76]