LOWER CAMBRIAN. 55 
In this I can not agree with him. Dr. Torell’s name has priority; his 
description is sufficient to identify the species, and under the prevailing 
rules of nomenclature it should be retained... And I find that Mr. Matthew 
is of the same opinion. To change all specific names that are not strictly 
descriptive or appropriate would lead to endless confusion and to more or 
less injustice to authors. 
Dr. Nathorst points out the differences between MW. radiata and Proto- 
lyellia princeps, calling attention to Dr. Linnarsson’s having probably 
described two forms under Astylospongia radiata.’ For the form with a 
round circumference, a region in the middle without structure, and having 
elevations resembling strings of pearls radiating toward the center, the name 
radiata is retained. The other form, Dr. Torell’s P. princeps, is also round, 
strongly convex on one side, slightly convex on the other; the surface of 
the latter has a structure of irregular cells or spaces, formed by sharp 
elevations anastomosing with each other, that lack the string-of-pearls 
appearance of M. radiata. This structure is generally absent from a 
more or less well-defined central space, which is usually raised above 
the cellular part. 
Dr. Nathorst states that the floor of the gastric cavity of Cyanea capii- 
lata is circular and divided by deep furrows into polygonal spaces; and the 
casts show polygonal cells surrounded by sharp edges. From this resem- 
blance, which he fully discusses, he refers the fossil form to the acraspedote 
medusz and the family Cyaneide. 
I have before me several good specimens of M. princeps, received from 
Dr. G. Lindstrém and from the Geological Survey of Sweden, that show 
the characters described. As yet I do not know of any similar forms from 
American Cambrian rocks. 
1 Kongl. svensk. Vet.-Akad. Handl., Vol. XIX, No. 1, p. 20. 
