ee, FOSSIL MEDUS 4. 
As in Hexarhizites, there are three zones which can be distinguished—an inner 
or genital zone; a median, smooth zone, and an external marginal zone. 
The mid-field shows a strong, bowl-shaped excavation, which plainly corresponds 
to the gastral cavity. Its periphery is circular, but appears to be octagonal. with 
rounded corners, if one regards as 1ts boundary points the points of contact of the 
genital pouches and the stomach pouches. In the central part of the mid-field, where 
it is most depressed, is the central mouth opening, surrounded by four oral arms 
which are thrown outward to one side, over the edge of the umbrella. 
Arms appear as convex rolls, considerably elevated. They do not reach the 
edge of the slab, but only about as far as the marginal tentacles. 
In the peripheral portion of the bow]-shaped mid-field arise eight radial ridges of 
about 2™" width, which gradually ascend from within outward until they reach the 
steep peripheral descent of the genital zone, and here end in the form of eight convex 
knots or papille. These papille are the most elevated portion of the fossil, and 
should therefore correspond to the thickest portion of the medusa disk. Each papilla 
has about the shape of a three-sided pyramid with a blunt point. By a more exact 
inspection of the mid-field and the adjacent genital zone, one is convinced that the 
eight areas (of the shape of an isosceles triangle) which are dissected by the eight 
radial ridges are alternately different. Four wide triangles alternate with four nar- 
nower. The latter are only very slightly narrower, but in their peripheral portion 
appear round, pit-like depressions, rather sharply defined, which are lacking in the 
areas alternating with these, and which without doubt are to be interpreted as genital 
cavities. The four narrower areas are interradial; the four broader ones alternating 
with them are, on the contrary, perradial, and, because of their concave nature, are to 
be regarded as gastral pouches. 
That the four broader areas which alternate with the genital fields are truly 
correspondent to gastral pouches can not be doubted ; while their peripheral rim is 
sharply defined by a convex curved line, and the middle part appears strongly exca- 
vated, their central end passes without interruption in the deep middle portion of the 
mid-field, into the stomach cavity. 
In the peripheral portion of the smooth zone there are poorly defined wrinkles 
which form fragments of concentric flutings, and are to be referred to the ring muscles 
of the subumbrella. Besides this, almost no especial structure is recognizable on the 
smooth zone. However, in certain lights, several very fine, straight, radial lines can 
be seen which persist through the whole width of the smooth zone and indicate 
radial canals. 
Since the families of this group are especially distinguished by means of the 
different character of the radial canals, and since just upon this very detail of char- 
acter no satisfactory degree of certainty can be attained, we will leave the question 
of its family relationship open here. It almost seems, however, that it can not be 
joined with any one of the known families. If this supposition proves correct, our 
fossil group can be called Lithosema, and the related family Lithosemxide. 
