BAHAMA MEDUSA. 7 



Specific Characters: The bell is thin-walled, about 0.75 mm. high and 

 0.3 mm. in diameter. The bell-walls are quite rigid and the velum powerful 

 and well developed. There are neither tentacles, radial canals, circular 

 vessel, nor marginal sense organs. The manubrium is spindle shaped and 

 about one- third as long as the bell-height. The fluids within the stomach- 

 cavity are maintained in rapid motion apparently through the action of cilia. 

 Near the aboral end of the bell there is a deep conical cicatrice which evi- 

 dently marks the place of last connection between the medusa and its 

 hydroid stock. The bell is translucent and milky in color while the manu- 

 brium is cream colored. Only five specimens, all males, were found in Nassau 

 Harbor, Bahamas, on the nights of July 18-19. They swam actively in arcs 

 of circles, but all died early in the morning although maintained in large 

 glass dishes filled with pure sea-water. They appeared to be mature, for 

 sperm was discharged constantly from the sides of the manubrium. 



This is the only free swimming hydromedusa, yet described, that lacks all 

 traces of tentacles, radial canals, and marginal sense organs. It is even more 

 degenerate than the medusae of Amalthaea and Pennaria, and may be com 

 pared with Eucopella ( R. von Lendenf eld, 1883 ; Zeit. fiir Wissen. Zool., Bd. 

 38, p. 497), and Agastra (0. Hartlaub, Wissen. Meeresuntersuch. Biologish. 

 Anstalt auf Helgoland, neu folge, Bd. 2, Heft 1, Abt. 2, p. 504, Taf. XXII, 

 Fig. 5, 8-10). In these remarkable medusae we find neither manubrium nor 

 marginal tentacles. There are, however, eight otocysts, and the radial and 

 circular vessels are well developed. 



Syndictyon angulatum, Mater. 

 Fig. 6, Plate I. 



Matbb, 1900; Bull. Mus. Comp. Zool. at Harvard Coll., Vol. XXXVII, p. 5, Figs. 6-8. 

 PL 3. 



The bell is 3 mm. high; half egg-shaped, with moderately thick walls, 



and becomes almost square in cross section when contracted. There are four 



slender tentacles with fairly thick spindle-shaped ends. These tentacles are 



each about as long as the bell height, and their distal halves are armed with 



nematocysts. The basal bulbs of the tentacles are not very large and each 



one bears an ocellus formed by a cup-like invagination of ectodermal cells. 



The velum is large, and the radial canals and circular vessel are of fine 



calibre. The manubrium is spindle-shaped with a narrow tubular oesophagus, 



