2 FOSSIL MEDUSA. 
The known geologic and geographic range of fossil medusze is shown 
in the following table: 
Table showing the known geologic and geographic range of fossil meduse. 
; ae : | 
| Jurassic ...-..---- | Bavaria. 
Permian. seer | Saxony. 
Middle Cambrian: Northern Alabama, U. S. A. 
Cambrian ....-.--- ‘2 Lower Cambrian: New York, U. S. A.; Lugnias, 
Sweden; Esthonia, Russia; Bohemia. 
List of species occurring at each horizon: 
Semostomites zitteli. 
Eulithota fasciculata. 
Acraspedites antiquus. 
Rhizostomites admirandus. 
Rhizostomites lithographicus. 
Leptobrachites trigonobrachius. 
Medusina deperdita. 
Medusina quadrata. 
Medusina bicincta. 
Medusina staurophora. 
Medusina cireularis. 
Medusina porpitina. 
IRENE, Go noon coagaboa nese ngoooodooseEoUasocmcaLC Medusina atava. 
os ( Brooksella alternata. 
= 4 Brooksella confusa. 
3 \ Laotira cambria. 
Oambriani- eee eee eee eee eee ere Dactyloidites asteroides. 
Medusina costata. 
Medusina princeps. 
Medusina radiata. 
PUTASSIO Me oe onic ote eionis oielaialoieloicte slot ieiaiscslsfelelsiste-tai= 4 
There is also to be considered the possibility that the Ordovician species 
Bythotrephis (?.) radiata Nich., from the Skiddaw slates, and Discophyllum 
peltatum Hall, from the Lorraine formation, are the remains of meduse. 
Of the evolution of the meduse, the fossil forms give little positive infor- 
mation. According to Haeckel, the Discomedusz were among the latest to 
develop of the Acraspeda. Geologically, their representatives appear in the 
