67S 



MEDUSAE OF THE WORLD. 



of the mouth-arms in addition to the terminal iluli, I have merged it with Mastigias for the 

 genera among Rhizostoniaia triptera are alrcad\ too numerous, and are distinguished upon 

 differences of such slight imponance that the disfinciions threaten to confuse rather than to 

 clarify the system of classification. 



Mastigias is closely allied to PseuJorbiza, but may be distinguished by its numerous, 

 complete, interocular radial-canals; whereas the converging vessels on the inner side of the 

 ring-canal between the 16 ladial-canals in Psftidorhiza end MiiidK without reaching the 

 stomach. 



The canal-system of von Lendenfeld's Ph\Uorhiza punctata is similar to that ot Mastigias, 

 but the mouth-arms bear numerous very long filaments without any definite terminal club. 



Ihe following synopsis of the forms of Mastigias may be of service, r is the length of 

 the radius of the exumbrella. 



Mastigias papua L. Agassiz. 



Cephta papua, Lr.ssoN, 1829, Voyage de la Coquille, Zooph., p. 1 22, planche 11, figs. 2, 3. 



Cepttfa papuemii, Grifhth, 1852, Cuvier's .Animal Kingdom, plate 3, fig. 3. 



Mastigias papua, Acassiz, L., i!i62, Cont. Nat. Hist. U. S., vol. 4, p. 152. — Haeckel, 1880, Syst. dcr Medusen, p. 623.— Maas, 



1903, Scyphomedusen der Siboga Expedition, Monog. if, pp. 66, 69, taf. 7, fign. 60, 62, 63; taf. 12, fig. ill. 

 Pseudorhiza thocamhaui, Agassiz, A., and Maver, 1899, Bull. Museum. Comp. Zool. at Harvard College, vol. 32, p. 173, plate 



13, figs. 40-44 (young stages). 

 Maslygias papua, Vanhofeen, 1902, Wisscn. Ergeb. deutsch. Tiefsee Expedition, Vahlivia, Bd. 3, Lfg. i, p. 47, taf. 4, fign. 



17-19. 

 Mastigias physophora, Kisiiinouve, 1891;, Zoolog. Magazine, Tokyo, vol. 7, No. 78, 3 pp., plate 13, figs. 1-13. — Schultze, L. S., 



1898, bcnkschr. Med. Nat. Gcscll. Jena, Bd. 8, p. 443. 

 Mastigias physopliora, Vanhoffen, 1902, Wissen. Ergeb. deutsch. Tiefsee Expedition, Dampfer Valdii'ia, Bd. 3, Lfg. 1, p. 49. 

 Mastigias papua var. pliysophora, Maas, 1909, .'\bhandl. Akad. Wissen. Munchen, Suppl. Bd. 1, .\bhandl. 8, p. 46. 



ikil ^o to 80 mm. wide, usually hemispherical, sonietiiiies flatter and sonietimes fuller 

 than a hemisphere. Gelatinous substance firm. Exumbrella surface with ver\- fine granu- 

 lations. 8 rhopalia, each with a |)igmented mass ot crystalline concretions and a shallow, 

 exumbrella, sensory pit without furrows. 80 marginal lappets. In each octant 2 small, 

 pointed, ocular and 8 larger, rounded velar lappets with deep furrows between them extending 

 a short distance up the sides of the exumbrella. Arm-disk somewhat wider than bell-radius. 

 The 4 subgenital ostia are about twice as wide as the columns between them and are each 

 somewhat constricted in the middle. Subgenital porticus unitary. 8 mouth-arms, each about 

 as long as bell-radius. The simple upper part 1.5 times as long as the 3-winged lower portion 

 ot the arm. The frilled mouths are developed not only along the edges of the 3 wings, but also 

 for some distance inward along the sides of each leaf. Each mouth-arm usualh' terminates 

 at its lower end in a club-like filament which may be as long as the diameter of the bell, but 

 is sometimes reduced in size or even wholly absent. This club is triangular in cross-section 

 and contains an axial canal. A large number of small, club-shaped vesicles arise from between 



