ZYGODACTYLA CYANEA. 



107 



Fi^'. 15S. 



Nahant, in company with the Z. groenlandica. The color of the males 

 is somewhat more pinkish than that of the females. 

 Massachusetts Bay, Nahant (A. Agassiz). 



Zygodactyla cyanea Agass. 



Zygodactyla cyanea Agass. Cont. Nat. Hist. U. S., IV. p. 361. 1862. 



This species is of a light-blue color ; can read- 

 ily be distinguished from Z. groenlandica by the 

 great thickness of the spherosome, and the large 

 digestive cavity ; the actinostome is bordered by 

 a number of very small and finely fimbriated 

 lips (Fig. 159) ; the chymiferous tubes do not 

 curve down and extend along the projection of 

 the spherosome in the inner cavity of the bell ; 

 at their highest point they empty into the diges- 

 tive cavity, the radius of which is more than one 

 half that of the spherosome itself, leaving but a 

 short space between the abactinal edge of the 

 digestive cavity and the circular tube ; the chy- 

 miferous tubes are numerous, ninety to a hun- 

 dred, usually placed opposite a long and exceed- 

 ingly contractile tentacle ; these are generally 



Fig. 158. Quarter of the disk of Z. crassa. 



Fig. 159. Portion of the disk of Zygodactyla cyanea, from the abactinal pole. 



