DISCOPHORA 325 



from the Cassiopeidae in the characters of the group. Ccjjhea is 

 found in the Indo-Pacific Oceans and Eed Sea. Cotylorhiza is 

 common in the Mediterranean Sea and extends into the Atlantic 

 Ocean. 



Group III. CvcLOMYArJA. — The group contains the majority 

 of the Ehizostomata. Musculature arranged in circular bands 

 round the disc. Oral arms primarily trifid, but becoming in 

 some cases very comy)licated. The principal families are : — 



Fam. Rhizostomatidae. — With well-marked epaulettes, and 

 sixteen radial canals passing to the margin of the umbrella. 



Rhizostoma pulmo ( = Pilcma octojyus), a widely distributed 

 species, is often found floating at the surface off the western 

 coasts of Scotland and Ireland, and sometimes drifts up the 

 English Channel into the German Ocean in the autumn. The 

 umbrella is about tw^o feet in diameter, and the combined length 

 of the umbrella and arms is four feet. The colour varies consider- 

 ably, but that of a specimen obtained off Valencia in 1895 was 

 described as follows : " The colour of the umbrella was pale green, 

 with a deep reddish margin. Arms bright blue." ^ 



The family includes Siomolojjhus, of the Pacific and Atlantic 

 coasts of America, in which the oral arms are united at the base, 

 and Rhoijilema, the edible Medusa of Japan and China. 



Fam. Lychnorhizidae. — Here there are only eight radial 

 canals reaching as far as the margin of the umbrella, and eight 

 terminating in the ring-canal. There are no epaulettes, and the 

 oral tentacles are often very long. The family includes Lychno- 

 rhiza from the coast of Brazil, Cramhione from the ]\Ialay 

 Archipelago, and Cramhessa from the Atlantic shores of France 

 and Spain and from Brazil and Australia. The last-named 

 genus has been found in brackish water at the mouth of the 

 Loire. 



In the families Leptobrachiidae and Catostylidae there are 

 eight radial canals reailiing the margin of tlie \imbrella, and 

 between them a network of canals with many openings into the 

 ring-canal. In a few of the Leptobrachiidae the intermediate 

 canal-network has only eight openings into the ring-canal, as in 

 the Lychnorhizidae. 



1 Proc. Hoy. Irish Acad. 3rd ser. v. 1900, p. 7-35. 



