Notes on Japanese Rhizocephala, with description of two new species

The following notes are based upon material of parasites on two Crustaceans from Japan, viz., Pachygrapsus crassipes Randall and Petrolisthes japonicus de Haan 1). Each of these two species may be infested by two different species of Rhizocephala: on Pachygrapsus crassipes occur the parasites Sacculina rotundata and S. confragosa, whilst Petrolisthes japonicus may be infested by the two species of Lernaeodiscus (cornutus and okadai) described in the present paper. I want to express my thanks to Professor Yaichiro Okada of Tokyo Normal College who collected a great deal of the material dealt with in the present paper at the sea shore near the Marine Biological Laboratory at Shimoda. I. The parasites of Pachygrapsus crassipes Randall. The two species which occur as parasites on Pachygrapsus crassipes are Sacculina rotundata Miers and Sacculina confragosa Boschma. In Sacculina rotundata the testes are found in the posterior part of the body (outside the visceral mass), the external cuticle bears excrescences of conspicuous size, each consisting of a basal part from which numerous spines arise (cf. Miers, 1880, Boschma, 1933). The type specimen was a parasite of Eriphia laevimana Latr., but the specimens on Pachygrapsus crassipes do not differ in any important detail from those living on Eriphia. In Sacculina confragosa the male genital organs are found in the visceral mass, the dorsal extremity of the testes is curved ventrally, the external cuticle is smooth, its surface divided into small areas which have a diameter of 8—18 µ (cf. Boschma, 1933). The only known host of this