JURASSIC. 79 
that his interpretation of this species as a rhizostome was correct, as his 
study of the living Crambessa tagi had given him renewed assurance of the 
correctness of the reference. He says: 
The oral under surface of the disk’s center, or, more exactly, of the umbrella 
stalk or oral disk, from whose periphery the four pairs of arms arise, shows in Cram- 
bessa tagi the same markings as in FR. admirandus, namely, a central mouth cross 
surrounded by eight isosceles triangular areas. However, the significance which I 
gave to these fields in Rhizostomites must be somewhat modified, for, as Crambessa 
plainly shows, the four major, convex isosceles triangles which touch in the center are 
not radial, but interradial. On the other hand, the four smaller, concave isosceles 
triangles whose points converge with the ends of the limbs of the mouth-cross are not 
interradial, but radial (more accurately, perradial). 
NOTES ON THE OBSERVATIONS OF DR. BRANDT! AND DR. AMMON ON RHIZOSTOMITES AND THE TWO 
SPECIES REFERRED TO IT. 
Dr. Brandt studied the material described by Dr. Haeckel and arrived 
at the conclusion that Rhizostomites admirandus and R. lithographicus were 
identical, the latter being only a younger specimen, as was suggested by 
Dr. Haeckel in his remarks on the species. This resulted from his observa- 
tions on the number of the marginal lobes, the width of the marginal zone, 
and the arrangement of the oral cross. Dr. Brandt believes that Dr. Haeckel 
was in error in his observations on the four crescentic mounds forming the 
crescent ring. Dr. Haeckel regards these as representing the genital 
pouches, but Dr. Brandt maintains that they are adventitious and without 
structural significance. He locates the genital arms in four radially 
located, depressed, elliptical figures, which Dr. Haeckel failed to observe. 
The fact that Dr. Haeckel regarded the fossils as secondary impressions, 
while Dr. Brandt believes them to be direct impressions, affords a basis for 
a definite interpretation of many of the future observations. 
Dr. Brandt calls attention to the fact that the configuration of the 
mid-field in R. lithographicus corresponds remarkably with that of Cram- 
bessa and must have the same significance. This is possible only on the 
theory that the fossil is a direct impression. He is also inclined to believe 
that Rhizostomites possessed, even at maturity, a mouth which was not 
closed by the growing together of the margins; in which event it would 
represent an intermediate form between the two acraspedote families. 
1 Ueber fossile Medusen: Mém. Acad. imp. sci. St. Pétersbourg, 7th series, Vol. XVI, No. 11, pp. 
1-18, Pl. I, fig. 1, 4. 
