536 THE VOYAGE OF H.M.S. CHALLENGER. 



that if Boeck's JEgma ecldnata should prove to be a ProtelJa, Haswell's Protella echinata 

 might be renamed erMnimana. 

 To the genus ^(jina, Ejciyer, Mayer assigns ^gina longicornis, Kroyer, with ^gina Ixvis, 

 Boeck, for a synonym; and ^gina ecldnata, Boeck, with the synonymy, Ai^gina 

 spinosisdma, Stimpson ; Caprella spinifera. Bell ; Caprella spinosissima, Bate, and 

 ? Caprella qnnosdssima, Norman. Of these, however, the first three represent ^gina 

 spinosissima, Stimpson, 1854, and the fourth is Caprella Jiorriila, Sars (see Note on Sars, 

 1885). As doubtful species oi JEgi^ia are mentioned Dana's "AJ aculeata" and "A. 7 

 tenella," from the Sooloo Sea, of which Dana thought the former might be the female, the 

 latter the male, of one and the same species. uSSginella, Boeck, distinguished from ^Eghia 

 only by having the appendages of the pleon unjointed, has the solitary species jEginella 

 spinosa, Boeck, also marked out by the strong dorsal spine at the beginning of the first 

 perEeon-segment. A spine on this segment is to be noted also in Caprella spimilafa, Couch, 

 1852. 

 In regard to the genus Caprella, Lamarck, Mayer calls attention, as Kroyer had already 

 done, to the great variability in the species, which has led to the introduction of 

 many needless specific names. He lays down a sort of canon, that " a single specimen of 

 small size can only be determined with any certainty under favourable circumstances." 

 New species ought not as a rule to be established without an opportunity of examining an 

 adult male specimen. Of about ninety named species Mayer has been able to refer ten to 

 other genera of CaprelUdas, about ten he has had to leave uninvestigated; of the remaining 

 seventy he has been able to recognise ten as undoubted species, the remainder consisting 

 partly of synonyms, partly of species perhaps good and tenable, partly of such as are 

 absolutely indefinite (uubestimmbar). His ten weU-ascertained si^ecies are thus classified: — 

 " A. Hinterfiihler mit Sinneshaaren. Dimorphismus bedeutend. 

 Stamm vollig glatt ; 2. Arm des erwachsenen Miinuchens lang. 



Hand desselben ausserordentlich gross und dick . C. graiuUmana, n. s. 



Stamm entweder auf alien oder wenigstens den drei letzten 



Segmenten mit jjaarigen oder unpaareu dorsalen Hockern 



oder Dornen ; 2. Arm des erwachsenen Miinnchens kurz, 



Hand desselben im Verhaltniss nicht so stark entwickelt 



wie bei der vorigen Art. . . . . C. acanthi/era, Leach. 



" B. Hinterfiihler mit Euderhaaren. Dimorphismus wechselnd. 

 Stirnstachel fehlt. 



Korper ungemein bestachelt. 2. Arm kurz. . . C. tuberculata, Bate and 



Westwood. 



— dorsal ganz glatt. 2. Arm kurz. . . C. lerjuilibra, Say. 



— nur auf Segment 5-7 bestachelt. 2. Arm des 



erwachsenen Miinnchens lang . . . C. linearis (Linne) Bate. 



Stirnstachel vorhanden. 



2. Arm des erwachsenen Mannchens kurz. 



Geissel des Vorderfiihlers mit 19-20 Gliedern . C. sep>tentrionalis, Kroyer. 

 Geissel des Vorderfiihlers mit 14 Gliedern. 



Kiemen liinglich. 5. und 6. Segment mit Hockern C. dentata, HaUer. 

 — rund. 5. und 6. Segment glatt . C. acutifrons, LatreiUe. 



2. Arm des erwachsenen ^Miinnchens lang. 



2. Hand desselben normal . . . . C. attenuata, Dana. 



2. — — ungewohnlich lang . . C. inermis, Haswell." 



To this table I have added the names of the authors of the species from the accounts given by 

 Mayer further on. 



