712 MKDUS^S OF THE WORLD. 



RHIZOSTOMATA SIMPLICIA Vanhoffen, 1888. 



ArMrhizids, HAF.CKEL, 1880, Syst. der Medusen, p. 565. CLAUS, 1883, Organisation uml Entwick. Mcdusen, Leipzig. VON 



LF.NDENFELD, 1888, Zeit. fur wissen. Zool., Bd. 47, p. 210. 

 Rhi'zostornata simphcia, VANHOFFEN, 1888, Bibliotheca Zoologica, Bd. i, Heft. 3, p. 39. 



These are probably only immature or torn and regenerating forms which are rendered 

 still more unnatural through shrinkage in alcohol. I present this account of them merely in 

 the hope that some may be rediscovered. At present they are wholly apocryphal. A des- 

 cription of the genera follows: 



Archirhiza HAECKEL, 1880. 8 free mouth-arms, 4 separate, subgenital cavities. 

 Haplorhiza HAECKEL, 1880. 8 free mouth-arms. A unitary, subgenital cavity. 

 Cannorhiza HAECKEL, 1880. Mouth-arms fused along their sides, forming a mouth-cylinder. 



Haeckel is the only naturalist who has seen any of these forms. They are all small and I 

 incline to the belief that they are merely immature stages or injured and regenerating 

 specimens of various other rhizostomae in the condition preceding the development ot the 

 ultimate ramuli of the mouth-arms. Vanhoffen (1902, Wissen. Ergeb. Valdivia Exped., Bd. 

 3, Lfg. i, p. 52) believes them to be merely mutilated medusae with the branches and appen- 

 dages of the mouth-arms lost or reduced. I have recorded them merely because they may still 

 have a place in literature if not in the ocean. 



Genus "ARCHIRHIZA" Haeckel, 1880. 



Archirhiza, HAECKEL, 1880, Syst. der Medusen, p. 565. VANHOFFEN, 1888, Bibliotheca Zoologica, Bd. i, Heft. 3, p. 39. 



GENERIC CHARACTERS. 



Rhizostomata simplicia with 8 simple separate, unbranched mouth-arms. With 4 separate, 

 subgenital cavities. With 16 radial-canals, some or all of which may give rise to anastomosing 

 side branches. The ring-canal gives off an anastomosing network of vessels which ramify 

 through the marginal lappets. The mouths have no appendages and are found only on the 

 ventral sides of the mouth-arms. 8 rhopalia. 



Haeckel founded this genus for Archirhiza primordialis from Bass Strait, Australia. Later 

 he describes another medusa, A. aurosa, from New Zealand, which is apparently only a later 

 stage in the growth of his A. primorJialis. Indeed, I suspect that both of these medusae are 

 immature, or "reconstructed" from fragmentary specimens. 



Archirhiza aurosa Haeckel. 



Archirhiza primordialis (young ?) , HAECKEL, 1880, Syst. der Medusen, p. 565, taf. 36, fign. I, 2. HAMANN, 1881, Jena Zeit. 



fiir Naturw., Bd. 15, p. 245 (anatomy of mouth-arms). VANHOFFEN, 1888, Bibliotheca Zoologica, Heft. 3, p. 39. 

 Archirhiza aurosa (mature ? ), HAECKEL, he. cit., p. 645. 



Young medusa ( ?). Bell flatly and evenly rounded, hemispherical in contraction, 2 to 3 

 times as wide as high when expanded. 40 mm. wide. Exumbrella finely granulated as in 

 Aurellia. 8 rhopalia, perradial and interradial. 48 marginal lappets. In each octant 2 large 

 median, flanked by 2 smaller velar lappets, and with 2 still smaller, rhopalar lappets flanking 

 the sense-organs. All of the lappets are pointed. Diameter of arm-disk two-thirds as wide 

 as bell-radius. 8 simple, separate, fleshy, unbranched, recurved mouth-arms arise in 4 pairs 

 on either side of each perradial corner of arm-disk. These mouth-arms lack appendages, 

 but there is a zigzag row of fringed mouths along the ventral side of each arm. These 8 

 lines of mouths of the mouth-arms fuse into 4 perradial lines over the mouth-arm-disk. The 

 mouth-arms are shorter than the bell-radius and are simitar-shaped, but fleshy and blunt at 

 their ends. 4 separate interradial genital sacs are invaginated into the stomach cavity, so the 

 arm-disk displays 4 interradial subgenital ostia. The central stomach gives rise to 16 radial- 

 canals, of which the 8 perradial and interradial canals give ofF branching side branches near 

 the bell-margin. The 8 adradial canals are simple. All 16 canals and their side branches fuse 

 with a well-developed ring-canal at the zone of the rhopalia, and on its outer side this ring- 

 canal gives ofFa close-meshed network of small vessels which anastomose through the marginal 

 lappets. Color ( ? ) Found in Bass Strait between Australia and Tasmania. 



