Notes on Meduse cf the Western Atlantic. 153 
white markings upon the surface were much fewer. These points of dif- 
ference were so important that it was concluded that this specimen must 
represent a different genus of Scyphomeduse. It was determined to be 
Polyclonia frondosa. Much time was spent in trying to find other speci- 
mens of the same form without avail.1_ The single individual found must 
have grown up in the moat from a larva brought in accidentally by the tide. 
The habit of these creatures is so excessively sedentary that it is incon- 
ceivable that the adult creature could have been carried thither by ocean 
currents. There may, of course, have been others in the same location, but 
the most painstaking search failed to reveal them, and this in spite of the 
fact that so large a part of the bottom is visible from a boat in clear weather. 
Oral scales —These noticeable flakes of white serve to distinguish the 
species at a glance from the evenly yellow hue of Cassiopea. Their presence, 
together with the absence of the digitate yellow appendages of Cassiopea, 
is sufficient, to my mind, to separate the genera from one another. The 
shape of these scales has been described. They are scattered over the arms, 
between forty and forty-five on each arm. They serve as little lids, guard- 
ing the openings into the oscula or oral funnels. They are sensitive to 
touch, contracting and bending away from anything that touches them. 
This reaction serves to bring the scale over the opening of the oral pores, 
preventing the ingress of the disturbing object. There is nothing in Cassi- 
opea which shows so great a degree of sensitiveness as these oral scales in 
Polyclonia. 
Oral arms.—Another point of difference was to be noted in the appear- 
ance of the oral surface of the two forms of Rhizostome, viz, the relative 
shortness of these processes in Polyclonia. In the individual examined the 
arms were not visible projecting beyond the disk, as in Cassiopea. Their 
length was a little less than the diameter of the disk. In Cassiopea, on the 
other hand, the oral arms project beyond the margin. 
Surface of disk.—There is a conspicuous band or ring of darker color 
in Cassiopea, three-fourths of the distance from the center to the margin 
of the smooth surface of the disk. It is just outside of a circle of large 
oval white spots, which are more or less sharply separated from one another, 
and it is bounded outwardly by a clean-cut band of whitish hue, which ex- 
tends to the margin. This ring is slightly raised above the rest of the sur- 
face, and when a jelly-fish is put into a glass jar it usually applies this part 
to the surface of the glass, the disk inside the ring and the margin being 
left free. The center of the disk is slightly concave, and acts, in this atti- 
tude, as a cupping organ. If one tries to remove the creature from its 
position, it will be found to require a vigorous pull to dislodge the disk from 
its hold upon the glass. The cells of the dark ring secrete mucus, which 
aids in giving a firm hold to the disk. 
“Dr. Mayer reports the finding of six individuals of this species in the moat 
during July, 1907. 
