LOWER CAMBRIAN. 47 
FOSSIL MEDUSZ OF THE LOWER CAMBRIAN TERRANES OF 
SWEDEN AND BOHEMIA. 
The interpretation of the fossils from the Lower Cambrian beds of 
Lugnas has been a subject of dispute among European paleontologists. 
Medusina radiata is first referred by Linnarsson to the sponges; but this 
view was abandoned by him later, after the appearance of Dr. Nathorst’s 
paper, in which it was referred to the medusze. Medusina princeps was 
referred by Dr. Torell to the corals; but this view was not accepted by 
those most familiar with this class of fossils, although Dr. Ammon had at a 
later date (1886) mentioned it and was inclined to place both M. favosa 
(M. princeps) and M. radiata in another division of the Ccelenterata. He 
Says: 
We do not regard it as possible that animals of such delicate constitution as 
the Aquorid could produce such sharp impressions in sandy deposits, and on no 
account is one justified, in view of the known material, in believing that in Cambrian 
time the class of Meduse was already differentiated into its two chief divisions, 
Acraspeda and Craspedota. 
To this Dr. Nathorst replies by referring Dr. Ammon to raindrop 
impressions on sand and also to artificial impressions of recent medusze 
figured in his memoir.* 
I think that the objection raised by Dr. Ammon, that the A2quoridz 
could not produce such sharp impressions in sandy deposits, arises from a 
misunderstanding. The impressions were made in a very fine silt or clay, 
and sand was washed into those impressions, producing the fossils described 
by Dr. Nathorst. As found in nature, there is a thin bed of shale on which 
rests a layer of sandstone or sandy shale, on the lower side of which the 
impression is found; or, if the fossil is free, it is formed of a fine sand and 
clay that was washed into the impression made on the soft clay which now 
forms the shale. Since the recent developments as to the extent of the 
differentiation of the Cambrian fauna, I do not think that strong objection 
could be made to the probable occurrence of the two chief divisions of the 
medusee in Cambrian time. 
Dr. Ammon claimed that Medusina (lindstrimi) costata could not be a 
‘Ueber neue Examplare von jurassischen Medusen: Abhandl. Math.-phys. Classe Kénigl. baye- 
rischen Akad. der Wiss., Vol. XV, 1886, pp. 160-161. 
?>Ueber cambrische Medusen: Zeitschr. Deutsch. geol. Gesell., Berlin, 1884, Vol. XXXVI, pp. 
177-179. 
