52 



BULLETIN OF THE BUREAU OF FISHERIES. 



great contraction, during which they are often characteristically coiled, ami with a broader base, 

 above which is a tubular, spur-like flap; numerous rudimentary tentacular bodies interposed between 



the long tentacles. Gonads in double-linear series along the 

 course of the radial canals, extending from slightly beyond 

 the gastric cavity to about the same distance from the marginal 

 canal. Manubrium almost lacking, gastric pouch very flat, 

 mouth a simple crinkled rim about the edge of the gastric pouch. 

 Otocysts numerous and variously interposed between the bases 

 of the tentacles. 



In general habits this medusa is sluggish, swimming lan- 

 guidly by only irregularly intermittent pulsations of the bell 

 margins. The velum is but poorly developed. It varies in size 

 from 25 to 70 mm., the average being about 40 to 50 mm. 

 Pntogeny wholly unknown. 



Distribution. — Not uncommon throughout the region, but 

 very erratic. During the summer of 1900 it was very abundant 

 at Woods Hole; in 1901 it was entirely absent; in 1902 a very 

 few specimens were taken. 



JEQUOREA Peron & Lesneur (1809). 



Tthegmatodes tenuis. 



-ffiquorea albida A. Agassiz. 



JEquorea albida A. Agassiz, in L. Agassiz Contributions Natural History of United States, Vol. IV, 1862, p. 359. A. Agassi/,. 

 North American Acalephse, 1865, p. 110. Haeckel, System der Medusen, 1879, p. 221. 



Bell somewhat less than hemispherical, tending to conical above. Radial canals very numerous, 

 80 to 100, or even more. Marginal tentacles, about three between each two adjacent canals, and each 

 with a superposed spur similar to Rhegmatodes. Manubrium better developed than in preceding, gastric 

 portion very flat and wide, mouth simple or somewhat crenulated when contracted. Gonads disposed 

 along the entire course of the radial canals. In size this medusa varies about as the preceding species. 

 Ontogeny entirely unknown. 



Distribution. — Not uncommon in and about Woods Hole during late summer and autumn. 



ZYGODACTYLA Brandt (1838). 

 Zyg-odactyla grcenlandiea ( Peron & Lesueur). 



Medusa sequorea, Fabricius, Fauna grcenlandiea, 1780, p. 364. 



jjp/nnn grxnlandica Peron *& Lesueur, Tableau dea Meduses, etc., in Annalesdu Museum, Vol. XIV, 1809, p. 339. 



Zygodaetyla grcenlandiea L. Agassiz, Contributions Natural History of United States, Vol. IV, 1862, p. 360. A. Agassiz, North 



American Acalepha?, 1S65, p. 103. 

 Tthacostoma atlantica, L. Agassiz, Proceedings Boston Society Natural History, Vol. Ill, 1862, p. 342. 

 Polycawna gra-nhnitlira Haeckel, System der Medusen, 1879, p. 232. 



This is one of the largest of the Hydromedusae, sometimes measuring a foot or more in diameter, 

 and about one-third as high. The bell is rather low and evenly arched above. Radial canals very 

 numerous, 100 or more. Marginal tentacles also numerous, like the preceding species, usually three 

 between each two adjacent canals, and with similar superposed spurs. Manubrium very large, extend- 

 ing beyond the bell margin; gastric portion very broad; oral portion comprising highly complex 

 plaited folds and frills. Gonads in double-linear series along the course of the radial canals. Ontogeny 

 unknown. 



Colors. — Manubrium, gonads, and tentacles dull whitish. 



Distribution. — Greenland (Fabricius). Maine to Massachusetts ( Agassiz). ( (ccasionally found in 

 Vineyard Sound and Buzzards Bay in late summer and autumn. 



