Abstract

The complete larval development of Leucosia obtusifrons DE HAAN, and the first zoeal stage of Arcania heptacantha (DE HAAN) and A. undecimspinosa HE HAAN are described and illustrated herein, compairing with those of the five species, A. undecimspinosa elongata Yokoya, Myra fugax (Fabricius), Philyra syndactyla Ortmann, P. pisum DE HAAN and L. anatum (Herbst). The larva of L. obtusifrons has three zoeal stages and one megalopa stage. In Myra and Arcania, five zoeal and one megalopa stages can be found. The larvae of philyrinid and leucosiinid crabs are classified into two groups by the following characters : 1) Group A : The maxilla II of the zoeae has 2・2 endopodal setation and the basal and coxal endites are bilobed. Megalopa bears the uropod in Myra and Arania. 2) Group B : The maxilla II of the zoeae has 2・1 endopodal setation, the basal and coxal endites are unilobed. Megalopa bears no uropod in Philyra and Leucosia.