RHIZOSTOM^ — AKCHIRHIZA, HAPLORHIZA, CANNOUIIIZA. 713 



It is highly probable that the medusa described above is only the young of the form 

 called Archirhiza mirosa, by Haeckel, from New Zealand. This is larger, being 50 mm. in 

 diameter. There are 80 instead of 4S marginal lappets. In each octant 8 oval, pointed velar, 

 between 2 small, triangular, rhopalar lappets. Mouth-arm conical, more pointed than in 

 A. primordialis, and 1.5 times as long as bell-radius. All 16 of the radial-canals give off 

 anastomosing side branches. 



Altogether, the differences between ,</. " prlmoyJialis" and A. aiirosa are precisely such 

 as one would expect to occur during the growth of the medusae. They are probably only young 

 stages of some species of Catostylus. 



"Genus HAPLORHIZA" Haeckel, 1880. 



Haplorhiza, Haeckel, 1880, Syst. Her Medusen, p. 604.— Vanhoffen, 1888, Bibliotheca Zoologica, Hi-ft. 5, p. 39. 



GENERIC CHARACTERS. 



Similar to Arclnrliiza but with a unitary subgenital cavity instead of 4 cavities as in 

 Archirhiza. 



This single, subgenital cavity or "porticus" is cruciform in shape and formed by the 

 fusion of the 4 primitive interradial genital sacs and the breaking down of the walls in the 

 fused regions, thus forming a cross-shaped cavity beneath the stomach. It is in communication 

 with the outer world through the 4 genital ostia, and is separated completely from the central 

 stomach. Its side walls constitute partitions between it and the central stomach and they 

 contain the genital products. 



Haplorhiza simplex Haeckel. 



Haplorhiza simplex, Haeckel, 1880, Syst. der Medusen, p. 604. 



Bell flat, shield-shaped, 40 mm. wide, 20 mm. high. 8 rhopalia. 48 marginal lappets. 

 In each octant 4 large, quadratic velar, between 2 tongue-shaped, projecting, ocular lappets. 

 8 simple, cylindrical mouth-arms, as long as bell-radius. 4 interradial, subgenital ostia, not 

 quite as wide as the arm-disk-pillars between them. 16 radial-canals and a ring-canal. Bass 

 Strait, southern Australia. 



This medusa is very briefly described by Haeckel, but in all respects it appears to be an 

 immature stage of some other rhizostomous medusa such as Catostylus. Its 8 simple mouth- 

 arms lack appendages and resemble those of the immature Archirhiza primordialis Haeckel. 

 The mouths are confined to the ventral sides of the mouth-arms. 



Haplorhiza punctata Haeckel. 



Haplorhiza punctata, Haeckel, 1880, Syst. der Medusen, p. 604. 



Bell flatly rounded, 40 mm. wide, 20 mm. high. 8 rhopalia. 176 marginal lappets, in 

 each octant 10 pairs of small, rounded velar lappets between 2 small, rhopalar lappets. 8 

 simple, cylindrical mouth-arms, hardly half as long as bell-radius, arise in pairs from the 4 

 perradial angles of the wide 4-cornered arm-disk. The frilled mouths are confined to the 

 ventral sides of the mouth-arms and there are no appendages. The 4 subgenital ostia are 

 3 times as wide as the columns between them. 



Exumbrella dark violet-brown, besprinkled uniformly with round white points. 



Arnheims Land, coast of northern Australia. This medusa is apparently immature. 



"Genus CANNORHIZA" Haeckel, 1880. 



Cannorhiza, Haeckel, 1880, Syst. der Medusen, p. 605. — Vanhoffen, 1888, Bibliotheca Zoologica, Heft. 3, p. 39. 



The type species is Cannorhiza connexa, Haeckel, from the neighborhood of New Zealand, 

 South Pacific. 



GENERIC CHARACTERS. 



Rhizostomata simplicia with 8 simple, unbranched mouth-arms, the sides of which are 

 fused one to another forming a hollow mouth-arm-cylinder, and leaving only the lower ends 

 of the arms free. There were neither clubs nor filaments upon the mouth-arms. There is a 

 unitary subgenital porticus. 8 rhopalia. The central stomach gives rise to 24 branching radial- 

 canals which fuse with a ring-canal. Peripherally the ring-canal gives off a network of vessels 

 which ramify through the lappets. 



