128 MARINE INVERTEBRATES 
Island Sound northward. It is from four to twelve inches high. The 
main stem is in long spiral turns, and at intervals has spreading plumose 
branches. The zooid-cups are tubular and closely pressed against one 
another, and are ranged in rows on one side of the branchlets; the aper- 
tures of the cups are plain and oblique. (Plate XLIII.) 
FAMILY GERYONOPSIDE 
Genus Tima 
T. formosa. A very delicate and transparent medusa; size one to 
two inches in diameter; bell conical; radial tubes four in number; 
manubrium long, hanging far below the disk; four frilled appendages 
diverging from the corners of the mouth; tentacles thirty-two; egg- 
sacs white and following the line of the radial tubes in undulating folds. 
This species is not very common; it is found on the New England coast. 
FAMILY EZQUOREIDE 
Genus Zygodactyla 
Z. groenlandica. Medusa 
seven to eleven inches in diam- 
eter; disk violet-colored and 
transparent ; margin fringed with 
long, fine, contractile tentacles of 
a darker violet color; numerous 
radiating tubes; egg-sacs in 
slightly waved plates; manubrium 
hanging below the line of the disk 
and with a thin frilled membrane 
depending from it. Found north 
of Cape Cod in July. 
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Zygodactyla groenlandica. 
ORDER TRACHYLINE 
The Trachymeduse are characterized by their direct develop- 
ment, the egg of the jellyfish producing a medusa and not a 
hydroid colony. 
Genus Trachynema 
Y. digitale. Size one inch to one and a half inches in height; rose- 
colored; the bell thin and hard, and conical at the top. The swimming 
is effected by contractions of the muscular velum (the band around the 
inner margin of the umbrella) instead of wholly by the bell. The ten- 
tacles are long and numerous, and are curled up when moving. The 
manubrium is long and has four expansions at the mouth. Eight egg- 
