68 



CTENOPHORA. 



2. Pleurobrachia pileus (O. f. Miiii.). 



? Beroe pileus. O. Fr. Miiller. Prodromus zoologise danicse. 1776. p. 232. No. 2817. 



? — — O. Fabricius. Fauna gronlaudica. 1780. p. 361. 



Cydippc bicolor. M. Sars. Beskrivelser og lagttagelser over nogle lUcerkelige eller iiye i Havet ved 



den bergenske Kyst ievende 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 Medusse of the Shores of 

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



— — Agass. A. Agassi z. North American Acalephae. 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. Ctenophoren d. Siboga-Expedition. 1903. p. 5. 



— rhodopis Chun. Moser. Ibid. p. 6. 



— pileus F^'abr. — 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. F'asc. I. 

 1909. p. 9. 



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



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

 the PI. pilnis of the European Coasts, nobody has hitherto doubted that the species PI. rhodopis estab- 

 lished l)y Chun for the Mediterranean form was really distinct, and judging from the literature there 

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

 (loc. cit.) it is seen to differ from PI. pilciis 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 lang. Scheide und Ten- Eiformig, Rippen ziemlich kurz. Scheide kurz. 



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

 Gefasse steil fiber 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 



Scheidenoffnung. 



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

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



