RHIZOST()M.«; — LKPTOBRACHIA. 



697 



between the ihopalia. Converging furrows extend up the sides of the exumbrella from the 

 clefis between the lappets. Arm-disk 4-sided, rarely as wide as the bell-radius, with subgenital 

 ostia 3 times as wide as the columns between them. A unitary, cruciform, subgenital cavit)-. 

 The 8 slender mouth-arms are about as long as the bell-diameter. The arms are triangular in 

 cross-section and end below in a triangular, pointed, naked extremity nearly one-founh as 

 long as the entire arm itself. 8 rows of frilled mouths radiate outward from a raised rosette 

 of frills at the center ot the arm-disk and extend down the ventral angle of each mouth-arm 

 for a distance about one-fourth the length of the arm. Below this the arm is naked, triangular, 

 and devoid of all mouths for about one-fourth of its length. Below this naked region are 3 

 double rows ot trilled mouths, i on the ventral and 2 on the dorsal angles of the arm covering 

 a length equal to about one-fourth the arm; below this region is the naked terminal club. Thus 

 from base to lower end we find : (i) a length wherein there are only ventral inouths; (2) a mid- 

 region devoid ot mouths; (3) a part wherein there are 3 double rows of trilled mouths, I ventral, 

 2 dorsal; (4) the pointed, naked, terminal club. There is a unitary marginal zone of ring- 

 muscles in the subumbrella. 



The cruciform, central stomach gives rise to 16 radial-canals, 4 perradial, 4 interradial, 

 and 8 adradial. All extend to the bell-margin and are connected by the ring-canal at some 

 distance inward from the margin. A network of anastomosing vessels connects the ring- 

 canal with the radial-canals on the inner side. On its outer side the ring-canal gives off a 

 forked canal into each velar lappet and a network of anastomosing vessels which connects 

 with all of the canals in the lappets. 



Found by the Challenger expedition near Juan Fernandez Island, off the Pacific coast ot 

 South America. 



Haeckel's " Leomira leptuia," from near New Zealand, is probably another name tor 

 L. terminalis. It differs only in having rectangular instead of pointed velar lappets and the 

 mouth-arms are 3 times as long as the bell-diameter, whereas the arms of L. terminalis are 

 said to be only about as long as the diameter of the bell. The "quadratic" marginal lappets 

 of L. "leptura" are probably due to the loss of their originally pointed ends, an accident which 

 frequently occurs to Scyphomedusae. 



It seems probable that Rhtzostoma leptopus of Chamisso and Eysenhardt, 182 1, is the 

 same medusa. It is described from the Radack Islands, tropical Pacific. The mouth-arms 



are not quite twice as long as the bell-diameter, thus resembling 



Haeckel's L. terminalis. 



The bell is light-violet, the margin and trilled mouths 



being darker. 32 reddish-violet spots on the exumbrella near 



the margin. Gonads yellow. 



RHIZOSTOMATA SCAPULATA Vanhoffen. 



Rhizouomata scapulaia, Vanhoffen, 1888, Bibliotheca Zoologica, Bd. 1, Heft. 5, p. 



42. — Maas, 1903, Scyphomedusen der Siboga Expedition, Monog. 1 1, p. 72. 

 5/omo/o/>A/(^.r+ /j;iKOj(omiW<r,CLALS, 1 883, Untersuch. liber Organisation und Entwick. 

 Medusen. — von Lendenfeld, 1888, Zeit. fiir wissen. Zool., Bd. 47, p. 208. 



Rhizostomje in which each of the 8 mouth-arms bears a 

 pair of wing-shaped outgrowths, called scapulets, or shoulder 

 ruffles which arise from the dorsal side of each arm near its 

 Fir.. 421.— Diagrammatic representa- point of origin fiom the ami-disk. Frilled mouths are devel- 

 tion of shape of mouth-arm in oped upon the Upper and outer sides of these scapulets as well 

 Rh,.os,oma,. scapulaia. ^^ ^^^^ ^^^ j^^^^ p^^^ ^j- ^^^ mouth-atms. The citculat 



muscles of the subumbrella are powerfully and the radial-muscles weakly developed or absent. 

 A description of the genera follows: 



Rhhoiioma Cuvier, 1800. 8 free mouth-arms, the lower parts of which are Y-shaped or 3-winged in cross-section. 

 These 3 -wings meet at a point at the lower end of the arm, and a naked, 3-cornered, club-like appendage arises from 

 this point. There are neither secondary clubs nor filaments upon the mouth-arms. 



Rhopikma Haeckel, 1880. Similar to RhizoHoma, but with numerous clubs or filaments upon the mouth-arms. 



Eupiltma Haeckel, 1880. Similar to Rhhonoma but there are neither clubs nor filaments upon the mouth-arms. 



Siomohphus L. .iVgassiz, libi^Brachiolophiis + Siomolophus Haeckel, 1880. 8 laterally coalesced mouth-arms form- 

 ing an 8-sided throat-tube for the central mouth. Lower ends of mouth-arms are free and branch complexly. 



