MEDUS/E. 



21 



Another species placed by Professor Haeckel in the genus Rathkea is Cytseis 

 octopunctata of Sars (1835). This species is fairly well known and has been found in 

 the Arctic regions and in the North Atlantic, along the coast of North America, and 

 also along the coast of Europe, from Norway to about as far south as the English 

 Channel. There is no evidence that the species occurs in the Mediterranean. Cytseis 

 octopunctata belongs to the genus Marc/ellium Haeckel. It has four radial canals, 

 eight groups of tentacles, and a peculiar mouth. The mouth has the appearance of 

 possessing four perradial. tentacles, each of which is distally bifurcated and terminates 

 with a small globular cluster of nematocysts. These are not true tentacles, but simply 

 the four corners of the mouth stretched out so as to resemble stalks. The clusters ot 

 nematocysts are really on the margin of the mouth and there is no mistaking their 

 position when the mouth is seen wide open. 



Rathkea fasciculata (Peron, 1809) is the third and last species mentioned by 

 Prof. Haeckel. This species is well known and has been described and figured by 

 Gegenbaur (1856), by Keferstein and Ehlers (1862) under the name of Lizzia koellikeri, 

 and by Leuckart (1856) under the name of Bougainvillia koellikeri. It was originally 

 named by Peron Mdicerta fasciculata, and was transferred by L. Agassiz (1862) to a 

 new genus called Koellikeria, because Melicerta was a pre-occupied name. This Medusa 

 has four radial canals, eight groups of tentacles on the margin of the umbrella, and 

 four perradial oral tentacles which are very much branched. The oral tentacles arise 

 a little way from the margin of the mouth, which has four lips without any clusters of 

 nematocysts upon them. The species is confined to the Mediterranean, and is well 

 known at Naples by the name of Lizzia koellikeri. 



I do not think that R. blumenbachi belongs to the same genus as R. fascicularis, 

 as Rathke's drawing of the mouth does not represent branched oral tentacles, such as 

 R. fascicularis possesses. It is also necessary to bear in mind that Rathke figured 

 eight radial canals. 



For the classification of the Margelidse it is necessary to know not only the 

 number of groups of marginal tentacles, but also whether the species has definite oral 

 tentacles (which may be branched or unbranched) or only clusters of nematocysts on 

 the margin of the mouth. Under the circumstances I think it is best to give Rathkea 

 fascicularis another generic name, and to place Rathkea blumenbachi on the dormant 

 list until we really know something more about it. There is not much to be gained by 

 retaining a badly described type species, as it only leads to confusion. 



1 think it will be an advantage to use in future the name Koellikeria for the genus, 

 and then fascicularis will become the type species. To this genus should be transferred 

 fi'dthkea octonemalis, Maas (1905), found at Ternate, and Lizzia elegans, Mayer (1900), 

 found off Tortugas, Florida. I am also rather inclined to include Chiarella centripetalis, 

 Maas (1897). Chiarella is distinguished from the other genera of the Margelidae by 

 possessing a double bundle of tentacles in each of the eight groups, and by having 

 interradial extensions of the circular canal, but these are almost too slight to be called 



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