408 A HISTORY OF EECENT CRUSTACEA 



(Pennant) (see Plate XVIII.). The specimens found were 

 in about one per cent, of the crabs examined. 



Portunion Salvatoris (Kossmann, 1881), on Portunus 

 arcuatus, Leach. 



Portunion Moniezii, Giard (1878), on Portunus puber 

 (Linn.). Excessively rare. 



Portunion Fraissei, Giard and Bonnier, 1886, on Por- 

 tunus holsatus, Fabricius. 



Portunion Kossmanni, Giard and Bonnier, 1886 (see 

 Plate XVIII.), on Platyoniclms latipes (Pennant). 



This is the only species that can be called common, 

 and one which does not necessarily sterilise the host or 

 hinder the exuviation of its integument. These are pro- 

 bably the conditions that have allowed it to become 

 common, since, when the parasite makes the host sterile, 

 it, so to speak, cuts the ground from under its own feet, 

 by preventing the propagation of the very animal which 

 is essential to the existence of the parasite's own progeny. 



Pinnotherion, Giard and Bonnier, 1889. Parasitic on 

 Pinnotheres. The first marsupial plate is without a trans- 

 verse lamella, and its recurrent part is of unusual length. 

 There are 110 dorsal ovarian humps, but of the ventral two 

 the hinder is excessively long and cylindrical, with 

 vermiform movements, whence the type species is called 

 Piwnoth erion vermiforme. 



Family 7. Bopyridce. 



The animals are parasitic in the branchial cavity, with 

 a few exceptions. The females in general have a flattened 

 appearance with one side longer than the other. Giard 

 and Bonnier, as already mentioned, subdivide this family 

 into Phryxiens chiefly found on Macrura Anomala, loniens 

 on Brachyura, and Bopyriens on regular Macrura. In 

 the Bopyriens the pleon is very degraded in both sexes, in 

 the male a single piece without appendages, in the female 

 shorter than in the loniens and never carrying ramified 

 appendages. These latter on the other hand are the _rule 

 in the loniens, of which moreover the males sometimes 



