LEPTOMEDUS.E — ZYGODACTYLA, ZYGOCANNA. 



337 



Velum well developed. Diameter of stomach about four-sevenths as great as that of bell. 

 The stomach-walls are not capable of much extension and the mouth does not protrude beyond 

 velar opening. Mouth surrounded by crenulated and folded lips, which are as numerous as 

 the radial-canals. Gonads of very large size, occupying the whole lengths of the radial-canals 

 from periphery of stomach to bell-margin. They are complexly folded and hang down into 



Fig. 194. — Oral view of "Zygodactyla crassa," after A. Agassiz, North American Acalepha?. 



the bell-cavity. Papillae upon the subumbrella( ?) Bases of tentacles colored with a faint 

 greenish-blue tinge. Gonads slightly yellowish-green. Color of male gonads pinkish. 



This medusa was found by A. Agassiz in Massachusetts Bay, at Nahant, but has not 

 been observed since. Is it a variety of Z. granlandica ? 



Genus ZYGOCANNA Haeckel, 1879, sens. ampl. 



Z\gocanna+ Zxgocannota, Haeckel, 1879, Syst. der Medusen, pp. 214, 215. 

 Polyxenia (in part), Eschscholtz, 1829, Syst. der Acalephen, p. 118. 



The type species is Zygocanna pleuronola, described by Peron and Lesueur from the north- 

 ern coast of Australia under the name JEquovea pleuronota. 



GENERIC CHARACTERS. 



./Equoridae with forked or branching radial-canals, which arise at equal intervals from the 

 periphery of the stomach. With 8 or more lips. Manubrium without a peduncle. Develop- 

 ment unknown. 



Haeckel distinguishes Zygocanna with 16 or more branched radial-canals and Zygocan- 

 nota with 12 branched radial-canals. It seems best to unite these genera, adopting Haeckel's 

 first name, Zygocanna. Haeckel's system makes no allowance for the possible discovery of 

 medusae with 8 to ii, or 13 to 15, branched radial-canals. 



Very little is known of these medusae. Their radial-canals arise at equal intervals from 

 the periphery of the stomach and almost immediately bifurcate. The gonads are developed 

 upon the peripheral branches. 



Zygocanna is separated from Zygocannula by its lacking a gelatinous peduncle, which is 

 found in Zygocannula, but I am inclined to believe that Zygocannula is the mature stage of 

 Zygocanna. 



