LOWER OAMBKIAN. 



55 



Iii 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 th;it 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 M. radiata and Profo- 

 lyeUia princeps,. calling attention to Dr. Linnarsson's having probably 

 described two forms under Astylospongia radiata. 1 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 capil- 

 tata 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 fullv discusses, he refers the fossil form to the acraspedote 

 medusa? and the family Cyaneidre. 



I have before me several good specimens of M. princeps, received from 

 Dr. Gr. Lindstrom 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. 



•KoDgl. svensk. Vet.-Akad. Hand]., Vol. XIX, No. 1, p. 20. 



