EUEOPEAN FORMS OF THE CIEOLANIN^. 357 



show more or less conspicuous sexual differences ; among these 

 especially the antennulse afford good specific characters. Clypeus, 

 epimera of the thoracic segments, seventh thoracic legs, and last 

 abdominal segment show excellent specific characters, but scarcely 

 any sexual difierence ; finally, the shape of the " appendix mas- 

 culina" (second joint of the endopod) of second pleopoda differs 

 in all species. Specimens rather far from sexual maturity differ in 

 some features more or less from adults ; especially small males 

 difl"er generally from adult specimens of the same sex in the 

 structure of the antennulse, length of flagellum of auteunse, and 

 relative length of abdomen, while other features, as clypeus, 

 epimera, and shape of last abdominal segment, are nearly or 

 quite similar in immature and adult specimens. When good 

 material is at hand, it is possible to determine even half-grown 

 specimens with absolute certainty ; but great caution is always 

 necessary, as the animals are closely allied to each other and 

 far from easy to separate. It is not my intention to give very 

 detailed descriptions; in my papers from 1890 to 1895 at least 

 one of the sexes, and sometimes both, of five of the six species 

 have been described and illustrated by numerous figures. Having 

 obtained one new species, the hitherto unknown male of 

 E. inermis, the female of E. truncata, &c., I am able to commu- 

 nicate some further details ; besides, I shall attempt to furnish 

 two keys and shorter descriptions as practical as possible for 

 discrimination of the forms. 



Our knowledge of the geographical distribution of the species 

 described here is still imperfect ; especially the Mediterranean 

 has not been explored, and, for instance, the statements of 

 Grourret and Lo Bianco on the occurrence of -E". pulchra off the 

 southern coast of France and off Capri are not trustworthy. 

 It is even not improbable that some new species may be 

 discovered in the western part of the Mediterannean or on the 

 Atlantic coast of Spain and Portugal. 



Conspectus of the Sjjecies. 



I. 



A. Posterior margin of last abdominal segment rather 

 deeply emarginate, with two conspicuous movable 

 spines close to each other at each end. Epimera of 

 second to fourth thoracic segments produced into 

 rather long processes '[. E. spinigera, H. J. H. 



