LEPTOMEDUS.E MKLICEUTISSA, ORfHISTOMA. 211 



usually in the " Melicertissa" condition with only 2 tentacles and 3 sense-clubs in each octant, 

 while other parts of the rim of the same medusa are in the " Melicertidium " condition with 3 

 tentacles and 2 sense-clubs in each octant. 



Melicertissa malayica Browne. 



Melicertidium malayicum, MAAS, 1905, Craspedoten Medusen der Siboga Expedition, Monog. 10, p. 28, taf. 5, fign. 19-31. 

 Melicertissa malayica t BROWNE, 1907, Annals and Mag. Nat. Hist., scr. 7, vol. 20, p. 477. 



Bell flat, 32 mm. wide, 20 short tentacles in each octant, 160 in all. These tentacles are 

 only about one-tenth as long as the bell-radius and their outer ends are coiled. They have 

 slightly swollen basal bulbs. At the base of about every fourth tentacle there is an abaxial, 

 ectodermal, swollen ocellus. Altogether there are 40 to 48 of these ocelli. 



A number of small clubs arise from the margin between the tentacles. These are about 

 hall as numerous as the tentacles and are irregularly scattered around the margin. The cores 

 of these clubs are filled with entodermal cells, as in LaoJicea. A few small, coiled cirri, much 

 fewer than the clubs, arise from the margin, each containing an axial core of entoderm. 



Velum narrow. There are 8 straight, narrow radial-canals and a simple, slender ring- 

 canal. Stomach flat, without a peduncle and with 8 simple, folded lips. Gonads linear and 

 developed upon the sides of the proximal thirds of the 8 radial-canals, adjacent to stomach. 

 The gonads begin to develop when the medusa is 18 mm. wide. The ocelli at the bases of the 

 tentacles are black. (See figure 107, page 210.) 



Malay Archipelago, Ternate. 2 specimens found by the Siboga expedition. 



Genus ORCHISTOMA Haeckel, 1879. 

 Orchisioma, HAECKKL, 1879, Syst. der Medusen, p. 138. KELLER, 1884, Recueil Zool. Suissc, tome I, pp. 417, 418. 



The type species of this genus is Orchistorna pileus, described by Lesson (1845, p. 317, 

 plate 6, fig. i) under the name of Mesonema piletis. This species is believed to have come 

 from the west coast of Africa. 



GENERIC CHARACTERS. 



Thaumantiadz with more than 8 simple radial-canals which arise separately from periph- 

 ery of stomach. The gonads are situated upon the radial-canals. Numerous tentacles. 

 Cirri or marginal sense-clubs may or may not be present. 



Mesonema of Eschscholtz, 1829, is one of the yEquoridae, and hence this generic name can 

 not be applied to the type species of Orchistorna. 



Orchistoma pileus Lesson. 



Plate 25, figs, l to 4. 



Mesonema pileus, LESSON, 1843, Hist. Zooph. Acal., p. 317, planchr 6, fig. i. 



Orchisioma steenstrupii, HAEI KEL, 1879, Syst. der Medusen, p. 139, taf. 15, fign. 3-5. KELLER, 1884, Recueil Zool. Suisse, tome 

 I, p. 417. 



Bell flat-topped with vertical sides, 30 to 40 mm. in diameter. Gelatinous substance 

 thick. 64 short tentacles with well-developed, hollow, basal bulbs; these tentacles are shorter 

 than the bell-radius and are flat and ribbon-like, with hollow bulbs. About 100 small, solid, 

 straight cirri from the side of exumbrella at a short distance above the bell-margin (plate 25, 

 fig. 2). The entodermal cores of these cirri are connected with the entoderm of tin- circular 

 canal. There are about 400 dark-brown, entodermal ocelli upon the circular canal. Each 

 ocellus is provided with an ectodermal lens (plate 25, fig. 3). 



Velum narrow. There are 32 straight, narrow radial-canals. The manubrium is pro- 

 vided with a large peduncle fully half as wide as bell-diameter and not quite as long as wide; 

 it extends a short distance beyond the velar opening. The stomach is wide and shallow, and 

 there are 32 long, complexly crenated lips (plate 25, fig. 4). There are 32 short, swollen, 

 linear gonads, one upon each radial-canal very near its point of juncture with the stomach. 



In the female the gonads are cinnamon-color, lips sage-green, tentacles ocher-yellow, and 

 ocelli black. Other parts colorless. In the male, however, gonads, lips, and tentacle-bulbs 

 are dull blue-gray. 



