* 
JURASSIC. 75 
Family (>) PELAGID 4 Gegenbaur. 
Genus ACRASPEDITES Haeckel. 
ACRASPEDITES ANTIQUUS Haeckel. 
Pl. XLIV, fig. 2. 
Medusites antiquus Haeckel, 1865. Zeitschr. fiir wiss. Zoologie, Vol. XV, pp. 509-513, 
Pl. XX XIX, fig. 2. 
Acraspedites antiquus Haeckel, 1869. Zeitschr. fiir wiss. Zoologie, Vol. XTX, p. 559. 
Acraspedites antiquus Haeckel, 1880. System der Medusen, p. 647. 
Acraspedites antiquus Ammon, 1886.- Abhand]. Math.-phys. Classe Konig. bayerischen 
Akad. Wiss., Vol. XV, p. 157. 
Dr. Haeckel states that little besides the “ topography” of the specimen 
is preserved. An acraspedote or phanerocarpous medusa. 
This is shown by the apparent structure of the genitalia. In M. antiquus I 
regard as such the lobe-like projections of the inner indented circle, which, as in all 
acraspedotes, lie between the radial canals. In WM. deperditus, on the other hand, the 
genitalia appear in the gentle spindle-shaped swellings in the middle of the radial 
canals, the direct enlargement of which they produce, as with all craspedotes. 
J inclined to put VW. antiquus with the Pelagide because of the simple, unbranched 
radial canals, which, together with the marginal lobes, are 8 in number. If, however, 
the radial canals were branched, the minor forks not being preserved, this form would 
probably have to be placed with the Aurelidz or Cyanide. 
M. deperditus probably goes with the Trachynemidie, and bears a strong resem- 
blance to Rhopalonema. Both have eight equally strongly developed radial canals, 
somewhat swollen in the middle. I believe that I can support this opinion also by 
the fact that in Rhopalonema I find every radial canal accompanied and supported by 
a double band of cartilage in streaks of greater consistency, which in any case would 
tend to leave behind a distinct impression. The gelatinous mass of the umbrella also, 
as well with the Trachynemide as with the nearly related Aginide, is distinguished 
by an almost cartilaginous consistency, which renders them better adapted for pres- 
ervation in a fossil condition than most other medusz. One is then almost inclined 
to regard the broad ring which surrounds the circle canal as the flat, expanded, and 
pressed velum, which in the family of the Trachynemide is strikingly thick and 
strongly developed. Probably, however, here, as in M. antiquus, it is better to refer 
this ring to the thickness of the gelatinous mantle itself, which, of necessity in the 
case of an animal spread out flat and lying on the sea bottom, spread symmetrically 
during its gradual entombment, while the whole body was slowly and symmetrically 
compressed in the direction of the principal axis. In the case of M. antiquus, in which 
the ring surrounding the circle canal (and also the actual rim of the umbrella cavity, 
though much less broad) appears much more distinctly impressed, is this conclusion 
