LOWER CAMBRIAN. 47 



FOSSIE MEDUSAE OF THE LOWER CAMBRIAN TERRAXES 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 Limiarsson 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 medusae. 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. Amnion had at a 

 later date (1886) mentioned it and was inclined to place both M. favosa 

 (3/. princeps) and M. radiata in another division of the Coelenterata, 1 He 

 says : 



We do not regard it as possible that animals of such delicate constitution as 

 the iEquoridse 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 Medusre was already differentiated into its two chief divisions, 

 Acraspeda and Craspedota. 



To this Dr. Nathorst replies by referring Dr. Amnion to raindrop 

 impressions on sand and also to artificial impressions of recent medusae 

 figured in his memoir. 2 



I think that the objection raised by Dr. Ammon, that the ^Equoridae 

 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 

 medusae in Cambrian time. 



Dr. Ammon claimed that Medusina (lindstromt) cosiata could not be a 



1 Ueber neue Examplare von jurussischeu Meriusen : Abhandl. Math.-phys. Classe Konijjl. baye- 

 rischen Akad. der Wiss., Vol. XV, 1886, pp. 160-161. 



* Ueber oainbrische Medusen: Zeitschr. Deutsch. geol. Gesell., Berlin, 1884, Vol. XXXVI, pp. 

 177-179. 



