034 MEDUSA OF THE WORLD. 



Maas, 1903 (Syphomedusen der Sihoga Expedition, p. 89), proposes another system 

 based upon the character of the muscle-system of the suhunibrella, the presence or absence 

 ofocelH on the sense-clubs, the character of the canal-system and of the mouth-arms. Maas's 

 system is as follows: 



Jrcadomxaria: The subumbrclla muscles are arranged in feather-like arcs. Mouth-arms elongate and irregularly pinnate 

 in their branching. Rhopalia with ocellus and without an exumbrella sensory pit. Radial-canals twice as numerous 

 as the rhopalia and connected by an anastomosing network of vessels. One or more ring-canals may or may not be 

 present. 4 separate genital sacs, with small, round, interradial ostia. There is only one family, the Casiiopeidtt. 



Radiomxaria: Radial-muscles of the subumbrella better developed than the circular muscles. Mouth-arms bifurcated. 

 Rhopalia without ocelli and without exumbrella, sensory pits. 8 principal and other secondar)* radial-canals, all 

 connected by a marginal network. No definite ring-canal. Funnel-shaped genital ostia. A unitary subgenital 

 cavity may or may not be present. There is one family, the Cepheidit, 



Cyclomyaria: Circular muscles of the subumbrella better developed than the radial-muscles, the latter being often absent. 

 Mouth-arms j-winged, or derived from this type. There are t; groups of the Cyclomyaria, as follows: 



{A) 16 radial-canals which extend from the stomach to the bell-margin, and between them a blindly-ending, anastomosing 

 network of vessels. Mouth-arms with scapulets. Genital ostia slit-like and divided by a median flap. Rhopalia 

 without ocelli, but with sensory pits with radiating furrows. Group A is equivalent to the Rbizostomida+ Stomo- 

 lophidtr of Claus, or to the Rhizostomata scapulatn of VanhofTen. 



{B) 8 rhopalar canals extend to the bell-margin and 8 in the intcr-rhopalar radii end in the ring-canal. On its outer 

 side, the ring-canal gives oflt a network of anastomosing vessels, and on its inner side it gives rise to another network 

 which ends blindly without connecting with the stomach. 



(1) Mouth-arms 5-winged, usually with pinnate lateral branches. Genital ostia slit-like. Rhopalia with pigment 

 spots, and sensor)' pits with radiating furrows. This contains the family Lychnorhizidic of Claus; including 

 the genera Lychnorhiza, C.rambione, and Crambessa. 



(2) Mouth-arms very elongate, triangular in cross-section. Genital ostia wide openings. Rhopalia with pigment 

 spots and furrowed sensorj- pits. This contains a part of Clauses family Leptohrachidit. 



(C) The 8 rhopalar extend to the bell-margin, and (8Xn) canals extend only to the ring-canal. On its outer side the 

 ring-canal gives off a narrow network and on its inner side is a network of wider mesh. 



(i) Mouth-arms very elongate, triangular, file-shaped. Genital ostia wide slits. Genera: Thysanostoma, Leplo- 



brachia, and Himanostoma of Claus's Lcptobrachidar. 

 (2) Arms 3-winged, not elongate. Ostia wide. Rhopalia with ocelli and small sensory pits without furrows. 

 This is equivalent to Claus* family Catostylida containing the genera Loborhiza, Crossostoma, and Mastigiai. 



The Arcadomyarta of Maas is only a new name for VanhofFen's Rhizostomata pinnata, 

 the Radiomyaria are equivalent to VanhofFen's Rhizostomata dichotoma, and the C\cIom\aria 

 includes rather confusedly the tr iptcr a •\' trigonal- scapiilata-\-lorif era of Vanhoften. Maas's 

 system is erroneous in some respects; for example the rhopalia of Cassiopea xamachana have 

 pigment spots while those of Cassiopea frondosa have none; similarly Crambessa tagi has 

 ("ocelli") pigment spots but Crambessa mosaica has none. It is therefore evident that the 

 presence or absence of **ocelli" does not afford a suitable criterion for the separation even 

 of genera. The exumbrella sensory pits may have furrows in one species of a genus and 

 be simple in another, as in Rhopilema esculenta and R. verillii. In my opinion the older and 

 simpler system of Vanhtiffen is to be preferred to this complex scheme proposed by Maas. 



In view of the observations of Schultze and of Maas, we may amend Vanhciffen's system 

 as follows: 



Rhizostomata pinnata: Rhizostoma; with 8 separate, elongate, linear mouth-arms which give rise to pinnately or com- 

 plexly arranged side branches (figs. 4. 5, and 7, plate 69). The circular muscles of the subumbrella tend to be 

 bowed outward in a scries of arcs on both sides of each radial-canal, the convexities alternating with the canals. The 

 genera arc as follows: Toreuma Hakckel, 1880, with 8 rhopalia. 

 Cassiopra PtRON and LrsuF.tR, 1809, with more than 8 rhopalia. 

 Rhizostomata dichotoma: 8 separate mouth-arms, the lower parts of each one of which is V-shaped in cross-section, the 

 apex of the V being ccntrad, and the rays directed outward (fig. 404, p. 6^0) The mouths are developed upon the 

 ventral sides of the mouth-arms. The radial-muscles arc powerfully, and the ring-muscles weakly, developed. The 

 radial-canals arc all connected by a marginal network of vessels, without a definite ring-canal. The genera arc as 

 follows: 



Cephea PtRON and Lesltifr, 1809. Exumbrella with a central dome bearing solid, wart-shaped protuberances. 

 Cotylorhiza L. Agassiz, 1862. With a smooth, simple dome at the center of the exumbrella. 

 Polyrhiza L. Agassiz, 1862. Exumbrella with a central depression and with radiating furrows. 

 Rhizostomata triptera: 8 separate mouth-arms the lower parts of each of which is Y-shaped in cross-section, due to the 

 development of 2 lateral, dorsal, and a median ventral, longitudinal lamella, all ^ of which taper to a point at the 

 lower end of the arm. The mouths are developed upon the free edges and partially over the sides of the 3 lamella; 

 or wings of the mouth-arms (fig. 41 1, p. 664) The ring-muscles are powerfully and the radial-muscles weakly, devel- 

 oped. A ring-canal with a network of anastomosing vessels arising from its inner and outer sides is usually present. 

 Mouth arms without scapulets. The genera are very closely related and are as follows: 



Catostylus L. Agassiz, iS(>2^Toxoclytus+ Crambessa Hakckel. Mouth-arms without filaments, clubs, or other 

 appendages. The network of vessels arising from the inner side of the ring-canal ends blindlvj without con- 

 necting with the stomach. 

 Lychnorhiza Hakckel, 1880. With filaments but without clubs upon the mouth-arms. In other respects similar 

 to Crambessa. 



