92 MEDUSA OF THE WORLD. 



the bell-height, while the other is only about two-thirds this length. Each of these tentacles 

 terminates in a club-shaped, nematocyst-beanng end. The small tentacle gives rise to 2 to 3 

 side branches while the large one gives rise to 4 side branches. These side branches arise 

 from the outer (aboral) side of the tentacle, and each one terminates in a knob-like end con- 

 taining nematocysts as in the end of the main shaft itself. The youngest and least-developed 

 side branch is always found nearest the side of the bell, whereas the oldest is nearest the outer 

 end of the tentacle. The basal bulbs of the tentacles are large and swollen and contain each 

 an ectodermal ocellus upon the outer (abaxial) side of the bulb. The ectodermal core of each 

 tentacle and of the side branches is hollow. The nematocyst bulbs of the tentacles are 

 provided with delicate bristles. The velum is quite narrow. There are 4 straight, simple 

 radial-canals and a narrow circular vessel. The manubrium is flask-shaped, and cruciform in 

 cross-section, with 4 small, cruciform, nematocyst-covered lips. The stomach-cavity does 

 not project upward into the gelatinous apex of the bell. The gonads are developed upon 

 the interradial sides of the stomach. 



The entoderm of the manubrium and the circular and radial-canals is dull ocher-yellow, 

 while the entodermal cores of the terminal bulbs of the tentacles is of a brighter yellow. 



The 4 ocelli (2 on the bulbs of the well-developed tentacles and 2 on the rudimentary 

 tentacle-bulbs) are dark reddish-brown. 



This medusa is occasionally found at Tortugas, Florida, from May until July. It is 

 taken each year upon the surface, but never in large numbers. 



This species is widely separated from other medusae of the genus Gemmana by its well- 

 developed ectodermal ocelli upon the 4 tentacle-bulbs and by the total absence of nematocyst 

 tracts upon the exumbrella. The "filaments" arising from the abaxial sides of the 2 long 

 tentacles are almost as thick as the main shaft of the tentacle itselt, and in comparison with 

 species of Gemmaria they are greatly reduced in number. This numerical disparity is, how- 

 ever, counterbalanced by their great size. 



Genus PTERONEMA Haeckel, 1879. 



Microstoma, preoccupied by CUVIER, 1817, for Fishes. 



Microstoma, LESSON, 1829, Voyage autour du monde sur la Coquille, tome 2, Zooph., p. 130. 



Pteronema, HAECKEL, 1879, Syst. der Medusen, p. 101. VANHOFFEN, 1891, Zool. Anzeiger, Jahrg. 14, p. 445. 



The first medusa to be described which belongs to this genus is Microstoma ambigua 

 Lesson, from New Guinea. 



Haeckel, 1879, describes that which is probably the same medusa, in an expanded state, 

 under the name Pteronema darwinii. This species is described from the coast of Australia, 

 but the exact locality is not stated. 



GENERIC CHARACTERS. 



Similar to Zanclea, but distinguished by having a brood-sac above the stomach, the 

 nature of which is unknown. If it be similar to that of Eleutlieria it has no connection with 

 the stomach. Haeckel considers it to be continuous with the stomach, but his studies do 

 not demonstrate this to be true, for he cut no sections. 



There are no meridional tracts of nematocysts upon the exumbrella in Pteronema. 



Pteronema darwinii Haeckel. 



( ? ?) Microsioma ambigua, LESSON, 1830, Voyage de la Coquille, Zooph., tome 2, p. 130, plate 14, figs. 5, 5'. 



(? ?) Microslotna ambiguus, LESSON, 1843, Hist. Zooph. Acal., p. 295. 



(? ?) Zanclea ambigua, AGASSIZ, L., 1862, Cont. Nat. Hist. U. S., vol. 4, p. 344. 



Pteronema darwinii, HAECKEL, 1879, Syst. der Medusen, p. IOI, taf. 7, figs. I, 2. 



(? ?) Pieronema ambiguum, BEDOT, 1905, Revue Suisse de Zool., tome 13, p. 144 (literature, 1830-1850). 



Haeckel describes his Pteronema darwinii from a single specimen preserved in glycerin. 

 He states that the preservation was good, but that the tentacles were contracted and are 

 represented in his figure as being of double the length observed in the preserved specimen. 

 This medusa was obtained somewhere ofF the coast of Australia. 



Lesson, 1830, describes a medusa under the name Microstoma ambigua from Waigion, 

 New Guinea, which may possibly be identical with P. darwinii. Lesson's description is, 



