Petasma
The copulatory organ of the male species located ventrally on the thorax between the bases of the two posterior pairs (4th and 5th) pereiopods. It is formed from both the first left and right anterior abdominal pleopods. The stiff tubular process is used for transferring sperm packet to the thelycum of the female.

Thelycum
The copulatory organ of the female species located ventrally on the thorax between the bases of the two posterior pairs (4th and 5th) pereiopods. It consists of an anterior, a posterior and sometimes lateral plates. This seminal receptacle is used to store spermatophore transferred from the male.