406 A HISTORY OF RECENT CRUSTACEA 



These are in reality ectoparasites, thougli with an ap- 

 pearance of being endoparasites. The sheath or enveloping 

 membrane moulded on every detail of their bodies is an 

 invagination of the hypodermis of the crab in which the 

 Entoniscid lives. 



JEntonisGns, Fritz Miiller, 1862. Parasitic on Porcel- 

 lanidae. The female has the marsupium open when adult, 

 with deeply cut edges to the component plates, and an 

 elongate pleon with five pairs of sabre-shaped pleopods. 

 The male is comparatively large, with the first antennae 

 elongated, six pairs of trunk-feet reduced to pedicellate 

 tubercles, and the last segment of the pleon not slit. 



Entoniscus 2^07xellance, Miiller, 1862, on Porcellana sp. 



'EntonisGus Miilleri, Giard and Bonnier, 1886, on Por- 

 cellana longicornis (Linn.). 



JEntoniscns hrasiliensis, Miiller, 1871, on Porcellana sp. 



Entoniscus Cre]^jlmiij Giard and Bonnier, 1887, on Po7'- 

 cellana (Polyonyx), Greplmii^ Miiller. Fritz Miiller found 

 a couple of the Porcellana in almost every tube of the 

 Clueptopteri at Desterro. Only three times did he find 

 the Porcellana solitary', once a female, twice a male. Only 

 on these three specimens did he find an Entoniscus. The 

 parasite makes the animal sterile, and it is inferred that 

 the infested crabs either could not find or retain partners. 

 Possibly they did not make the attempt to do either one 

 or the other. 



Entione^ Kossmann, 1881. The male has the last 

 segment of the pleon terminally bifid. This genus siuce 

 its institution has been much subdivided, and the original 

 name limited to Entoniscidae parasitic on Oxyrrhyncha. 



Entione acJuEi, Fritz Miiller, on Acluvus sp. 



Grapsion, Giard and Bonnier, 1886. Parasitic on 

 Grapsida3. The female has the marsupium closed when 

 adult, the ascendant lamella of the first pair of marsupial 

 plates narrow all along ; there are two medio-ventral and 

 two latero-dorsal ovarian bosses and four dorsal tubercles ; 

 the pleopods lamellar, little recurved. The male has the 

 sixth segment of the pleon ending in two recurved hooks. 



