58 CTENOPHORA. 



2. Pleurobrachia pileus (o. F. MM.). 



? Beroe pileus. O. Fr. Mtiller. Prodromus zoologise danicEe. 1776. p. 232. No. 2817. 



f O. Fabricius. Fauna gronlandica. 1780. p. 361. 



Cydippe bicolor. M. Sars. Beskrivelser og lagttagelser over nogle mserkelige eller nye i Havet ved 



den bergenske Kyst levende Dyr. 1835. p. 35. Tab. 7, fig. 17. 



Pleurobrachia rhododactyla. L,. Agassiz. Contributions to the Natural History of the Acalephse of 



North America. II. The Beroid Medusae of the Shores of 

 Massachusetts. (Mem. Amer. Acad. N. Ser. IV. 1849). 

 Agass. A. Agassi z. North American Acalephse. 1865. p. 30 33. 

 rhodopis. Chun. Ctenophoren d. Golfes v. Neapel. 1880. p. 282. Taf. II. Fig. 5 6. 

 pileus Fabr. Vanhoffen. Die gronlandischen Ctenophoren. 1895. p. 21. 



Chun. Ctenophoren d. Plankton-Exped. 1898. p. 15. 

 aut. Romer. Die Ctenophoren. Fauna arctica. III. 1903. p. 70, 75. 

 Fabr. Vanhoffen. Ctenophoren. Nordisches Plankton 1903. p. 3. 



Moser. Cteuophoren d. Siboga-Expedition. 1903. p. 5. 

 rhodopis Chun. Moser. Ibid. p. 6. 



pileus Fabr. Ctenophoren d. deutschen Siidpolar-Exped. 1909. p. 141 146. 



(F.) A. Ghigi. Ctenofori. Raccolte planctoniche fatte della R. Nave "Liguria" 



nel viaggio di circumnavigazione del 1903 05. Vol. II. Fasc. I. 

 1909. p. 9. 

 rhodopis Chun. A. Ghigi. Ibid. p. 9. 



While it is generally agreed that the PI. rhododactyla of the American coasts is identical with 

 the PL pileus of the European Coasts, nobody has hitherto doubted that the species PL rhodopis estab- 

 lished by Chun for the Mediterranean form was really distinct, and judging from the literature there 

 should be no difficulty in distinguishing it from PL pileus. After the diagnosis given by Chun 

 (loc. cit) it is seen to differ from PL pileus among other characters in the meridional vessels being 

 voluminous and "nicht scharf von den adradialen Stammen abgesetzt". Moser (Siboga-Ctenophoren, 

 p. 30) gives the following differential diagnoses of the two species: 



PL pileus. PL rhodopis. 



"Eiformig, Rippen laug. Scheide und Ten- Eiforrnig, Rippen ziemlich kurz. Scheide kurz. 



takelbasis ziemlich lang. Eintritt der adradialen Tentakelbasis nicht lang. Eintritt der adradialen 

 Gefasse steil iiber dem Trichter im aboralen drittel Gefasse auf gleicher Hohe mit dem Trichter, in 

 der Rippe. Dariiber die Scheidenoffnung. der Mitte der Rippe, auf gleicher Hohe die 



Sch eidenof f nung. 



The colour is thus given by Chun: "Durchsichtig, Tentakelbasis und Fangfaden rosa pig- 

 mentiert". In Moser: Ctenophoren d. deutschen Siidpolar-Expedition (p. 148) the species is mentioned 



