MAYER : MEDUS.E FROM THE TORTUGAS, FLORIDA. 27 



Morphology of Tortugas MEOuSiE. 



Among the new species described in this paper the following are 

 worthy of special notice : Pseudoclytia x^^f-tata, a hydromedusa, is 

 normally pentamerous, having 5 radial canals 72° apart, 5 gonads, and 

 5 lips to the proboscis. This curious species has probably been derived, 

 philogenetically, from a pentamerous sport of some form of Epenthesis, 

 and represents the survival of a discontinuous, meristic variation. 



Multioralis ovalis is a new genus of Hydromedusee iu which 4 sep- 

 arate manubria are situated upon a single straight chymiferous canal, 

 which traverses the long diameter of the bell. 



Eucheilota paradoxa is the only Leptomedusa known which gives rise 

 to young medusas by a direct process of budding. 



Niobia dendrotentacula is a remarkable form of Hydromedusa iu which 

 the tentacles develop into new meduste and are set free to propagate the 

 species. This is accomplished through a process of growth, budding, and* 

 fusion of parts. After all of the tentacles have been cast off, the adult 

 medusa reproduces by a sexual process. 



In Bougainvillia niobe, Mayer, the medusa buds found upon the 

 proboscis are formed entirely from the ectoderm, the entoderm taking 

 absolutely no share in their construction. 



Oceania McCradyi of Brooks, 1888, a hydromedusa that produces 

 hydroid-blastostyles upon its gonads, has been found at the Tortugas. 



In Dysmorphosa dubia, there appear to be 4 rudimentary gonads ? 

 upon the 4 radial canals. If future observations confirm this conjecture, 

 the case will be almost unique among Tubularian medusae. 



Summary of Results. 



There is at the Tortugas, Florida, a tropical Medusan fauna, only 

 three species of which are established upon the southern coast of New- 

 England ; and not one species of which is found upon the Il^ew England 

 coast north of Cape Cod. 



The Hydromedusa) of the Tortugas are more closely related to those 

 of the Fiji Islands, South Pacific, than they are to those of the Canary 

 Islands, off the Atlantic Coast of Africa. 



In comparing tlie Hydromedusan fauna of the Tortugas with that of 

 the Canaries, we see that the Leptoliua forms of the Tortugas are 

 almost wholly distinct from those of the Canary Islands. A number of 

 Trachylina forms are, however, common to the two groups of islands. 



VOL. XXXVII. — NO. 2. 2 



