78 FOSSIL MEDUS2. 
of the subumbrella. On the contrary, they are short, much broken, unequally 
separated one from the other, and for the most part bifurcate terminally and run out 
into several gradually disappearing and diverging delicate furrows. These furrows 
can very well be referred to the irregular furrows which exist between the super- 
ficial folds of the fourfold elevation formed by the genitalia in the Rhizostomide and 
other acraspedote medusze. . 
The third or smooth ring can be nothing else than that portion of the gelatinous 
disk which immediately surrounds the genital cavity, and, in fact, forms its outer 
wall. The compietely even and smooth surface of this ring corresponds to the simple 
nature of this portion of the umbrella, in which no especial structures are visible, and 
where even the ring muscles of the subumbrella, which characterize the fourth ring 
in so marked a manner, are lacking. Very important, too, is the negative cireum- 
stance that neither the smooth ring nor the two rings inclosing it are pierced and 
interrupted in a radial direction by the prolongations of the radial arms. It can be 
concluded from this that these were proportionally short and thick, similar to those 
in the living Stomolophus; even were they as long asin Rhizostoma and in most 
other Rhizostomid, they need not necessarily have overlain merely the inner ring 
(whose irregular figure they condition), but also the three outer rings. 
Beyond all doubt the 35 to 40 fine and concentric circular mounds which project 
as low, three-cornered, prismatic ribs over the surface of the rings and leave the same 
number of deep and sharp furrows between them, are to be referred to the muscle 
rings of the subumbrella, which, in many Rhizostomide, as well as in many other 
Acraspedee (especially Cyaneide), project in the form of strong, almost furrow-shaped 
muscle rings over the under surface of the subumbrella. The muscular rings begin 
in the outer portion of the smooth ring, become the strongest in the inner third of the 
furrowed ring, and from there gradually fade away, so that the periphery of the disk 
could only be contracted by comparatively weak ring muscles. The peripheral lobes 
amount to 128 in the cireuit of the entire disk. The very large number of these mar- 
ginal lobes, which are characteristic of the Acraspede, fits in especially with the 
character of the Rhizostomid, which are distinguished from the rest of the medusze 
by the especially large number of these. The entire absence of all appendages to the 
disk rim also speaks in a strong, negative manner for the rhizostomide nature of the 
meduse. As a last form-character of the umbrella rim, likewise excellently fitting 
our interpretation, can be offered the large, flat marginal lobes, which are indicated 
on the under side of the impression by the strong radial indentations (y;) and the 
interradial indentations (x). Both these invaginations, of which there must have 
been eight in the whole disk edge, were surely deep incisions in which the four radial 
and four interradial sense organs resided.! 
Dr. Haeckel next discusses the systematic position of this species, and 
refers it to the family Rhizostomidee 
In his review of the fossil medusze of the Jura, Dr. Haeckel? states 
' Neues Jahrbuch fiir Min., Geol. und Pal., 1866, pp. 273-280. 
2 Zeitschr. fiir wiss. Zoologie. Vol. XIX, 1869, p. 557. 
