[9] 



MEDUSyE from the gulf stream. 



DlSCOIDEA. 



Family VELELLIDiE. 



Velella mutica, Bosc. 



521 



Family PORPITID^. 



PORPITA LINN.EANA. 



Catalogue 

 number. 



Station. 



11640 2536 



11641 I 2537 



11642 | 2538 



11643 l 2566 



Craspedota. 

 Family JEQUOUIDJE, Eschscholtz. 



Pol yc anna, Hseckel. 



It is very difficult to distinguish the genera aud species of the above 

 familj', especially the American representatives. 



A. Agassiz describes three species of Zygodactyla from our coast: 

 Z. grcenlandica Ag., Z. crassa A. Ag., and Z. cyanea, A. Ag. Haeckel 

 places Z. grcenlandica, Z. crassa, and Cremastoma flava, A. Ag., in the 

 genus Polycanna, Hseckel, while Z. cyanea A. Ag. is referred to his genus 

 Mesonema as M. cyaneum. According to A. Agassiz, the tentacles in 

 Z. grcenlandica, Z. crassa, and C. flava are more numerous than the 

 cby miferous tubes. This is true also, according to Hseckel, of P. vitrina, 

 Hpeck. In P. germanica and P. italica, Haeck., the tubes and tentacles 

 correspond in number, while in P. fungina, Haeck., the radial tubes are 

 more numerous than the tentacles. These characters form the three 

 subgenera : 



1. Ehacostoma. Radial tubes more numerous than tentacles. 



2. Cremastoma. Radial tubes equal in number to the tentacles. 



