36 



IDYIA ROSEOLA. 



Idyia cucumis Less. 



Idyia cucumis Less. Zooph. Acal., p. 133. 1843. 

 Beroe cucumis Fab. Fauna Gronl., 1780, No. 353. 

 Beroe cucumis EscH. Syst. d. Acal., p. 36. 1829. 

 Medea fulgens Less. Zooph. Acal., p. 136. 1843. 

 Beroe cucumis MoRCH ; in Naturh. Bid. af Gronland, p. 98. 1857. 

 Idyia cucumis Agass. Cont. Nat. Hist. U. S., IIL p. 296. 1860. 

 ? Idyia horealis Less. Zooph. Acal., p. 134. 1843. 



The many species of Idyia which are described from the arctic parts 

 of the Atlantic Ocean, and which have been identified with Idyia 

 cucumis and Idyia horealis Less, by Professor Agassiz, are probably 

 all identical with the Beroe cucumis of Fabricius. 



Bafiin's Bay (Fabricius). 



Idyia roseola Agass. 



Idyia roseola Agass. Cont. Nat. Hist. U. S., HL pp. 270, 296, Pis. 1, 2. 1860. 

 Idyia roseola Pack. List of Animals dredged near Caribou Island. 1863. 



In the youngest Idyia which I have had the opportunity to observe 

 the digestive cavity, the eight ambulacral rows, the lateral chymiferous 

 tubes were already developed. When seen from above, the ambulacral 

 cavity has the shape of an eight-lobed rosette, with loops of different size. 



Fig. 52. 



Fip. 54. 



Fig. 53. 



occupying halt the space of the spherosome, seen m profile (Fig. 52), and 

 the whole when seen from the abactinal pole (Fig. 53). We are struck 

 by the immense size of the lateral tubes {I), and find that the inequality 

 in the lobes of the ambulacral cavity is caused by the greater size of 



In Iilyia, owing to a mistake in the lettering of the figures, c' is the long tube, and c the short 

 ambulacral tube, so that the lettering of Idyia does not exactly correspond to that of the other 

 young Ctenophorae. 



Fig. 52. Young Idyia, seen from the narrow side. 



Fig. 53. Fig. 52, seen from abactinal pole. 



Fig. 54. Young Idyia, in which the ambulacral tubes are distinct, seen from the narrow side. 



