712 meduSjE of the world. 



RHIZOSTOMATA SIMPLICIA Vanhoffen, 1888. 



Archirhhiddt, Haeckcl, 1880, Syst. dcr MeJuscn, p. 565. — Claus, 1883, Organisation und Entwick. MeJuscn, Leipzig. — von 



LrNDKNreLD, 188$, Zcit. fUr wisscn. ZooL, Bd. 47^ p. 210. 

 Rhlzosiomata timfhcla, VANHiirrEN, 1888, Bibliotheca Zoologica, Bd. i, Heft. 3, p. 39. 



These are prolialih- onlv immature or torn and regenerating forms which are rendered 

 still more uimatural through shrinkage in alcohol. I present this account ot them merely in 

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

 cription of the genera follows: 



Archirhiza Haeckci., 1880. 8 free mouth-arms, 4 separate, subgenitai cavities. 

 Haplorhiza Haeckel, 1880. 8 free mouth-arms. A unitary, subgenitai cavity, 

 Cannorhiza Haeckel, 1880. Moutli-arms fused along their sides, forming a moutli-cylindcr. 



Haeckel is the only naturalist who has seen an\- of these forms. The\' are all small aiui 1 

 incline to the belief that they are inerel\- immature stages or injured and regenerating 

 specimens of various other rhizostomse in the condition preceding the development of the 

 ultimate ramuli of the mouth-arms. VanhcifFen (1902, Wissen. Ergeb. VaUivia Exped., Bd. 

 3, Lfg. I, p. 52) believes them to he merely mutilated medusa; with the branches and appen- 

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

 have a place in literature if not in the ocean. 



Genus "ARCHIRHIZA" Haeckel, 1880. 

 Archirhiza, Haeckel, 1880, Syst. der Medusen, p. 565. — VANHotfEN, 1888, Bibliotheca Zoologica, Bd. 1, Heft. 3, p. 39. 



GENERIC CHARACTERS. 



RInzostomata simpUcia with 8 simple separate, unbranched mouth-arms. With 4 separate, 

 subgenitai 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 jirimorJialis 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 . primordlaVis. Indeed, I suspect that both of these medusae are 

 immature, or "reconstructed" from fragmentary specimens. 



Archirhiza aurosa Haeckel. 



Archirhiza primorjialis (young ?) , Haf.ckel, 1880, Syst. der Medusen, p. 565, taf. 36, fign. i, 2. — Hamann, 1881, Jena Zcit. 



fiir Naturw., Bd. 15, p. 245 (anatomy of mouth-arms). — Va.shofken, 1888, Bibliotlieca Zoologica, Heft. 3, p. 39. 

 Archirhiza aurosa (mature ? ), Haeckel, Ioc. cit.f p. 645. 



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

 times as wide as high when e.xpanded. 40 mm. wide. Exumbrclla finely granulated as in 

 AurcUia. 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-ann-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 invaginatcd into the stomach cavit\', so the 

 arm-disk displa\s 4 interradial subgenitai ostia. The central stomach gives rise to 16 radial- 

 canals, of which the 8 perradial and interradial canals give of!" 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. 



