MisceUaneoits. 235 



species must be'regarded as the types of two new genera, Proho- 

 pyrus and Palegyge *, from ■which are derived on the one hand the 

 Bo2Jyri and on the other the Gygce, which have been previously 

 described. We name t\i.evQ. Prohopyrus ascendens, Semper, and Pcde- 

 gyge Borrei, G. & B. 



Prohopy rus ascendens {Bopyriis ascendens, Semper) has already 

 been noticed by Semper t as a parasite of the branchial cavity of 

 Palmnon ornatus, Olivier, which, in the Philippine Islands, lives in 

 the brooks up to 4000 feet above the level of the sea. The genus 

 Probopyrus is distinguished from Bopyrus by the characters of the 

 pleon in the two sexes. In the female on the dorsal surface the 

 segments of the abdomen, although soldered together, are separated 

 by very distinct lines of demarcatioii, visible even at the middle of 

 the body. In the ventral part the pleopoda, instead of being re- 

 duced to a mere rudimentary plate on each side of the abdomen, 

 are formed by pairs of appendages homologous with those which we 

 have indicated by the letters h and c in Gepon and the loninae J. 

 This important character appears to have escaped the notice of Sem- 

 per, who figures simple abdominal plates (loc. cit. fig. 38) like those 

 of the typical Bopyri. In the male the pleon bears traces of lateral 

 appendages which are absolutely wanting in the Bojn/ri. Bopyrus 

 palcemoneticoJa, Packard (Bopyrus manhattensls, Gissler §), a para- 

 site of Palcenionetes vulgaris, Stimps., on the Atlantic coast of jSTorth 

 America, must also enter our genus Probopyrus, judging from the 

 figures given by Gissler. 



Probojiyrus ascendens difiers from Probopyrus jjalwmo^ieticola by 

 its larger size, the form of the pj-gidium of the female, that of the 

 pleal plates, &c. The presence of P. ascendens in the Dutch East 

 Indies considerably extends the habitat of this Crustacean. 



The second species that we have studied has received the name 

 of Palegyge * Borrei. It is with pleasure that we dedicate it to the 

 learned curator of the Brussels Museum, M. Preudhomme de Borre, 

 well known for his fine writings on the Arthropoda. We met with 

 it in the branchial cavity of PaJcemon dispar, E. von Martens ||. 

 Some ten specimens of this species were mixed with those of P. or- 

 natus in the Brussels Museum. Only one of them contained a 

 parasite, or rather a couple of parasites. 



The Palegygoi stand exactly in the same relation to Gyge as the 

 Probopyri to Bopyrus. They represent a less degraded ancestral 

 form, which has retained, in the structure of the pleon, the typical 

 organization of the loninae. In the characters of the foot-jaws, in 



* Sic ; recte Palo'gyge. 



t ' The Natui"al Conditions of Existence as they affect Animal Life ' 

 (1881), p. 147, fig. 38. 



X See Giard and Bonnier, ' Contributions a I'^tude des Bopyriens. — 

 Monographie du genre Cepon ' (1887), pl. i. 



§ Gissler, " A Singular Parasitic Isopod &c.," in ' American Natura- 

 list,' vol. xvi. (1882), p. 6, pis. i. and ii. 



II Prof. De Man, of Middleburg, has kindly aided us in the determina- 

 tion of this Palcemon. 



