Cambrian Faunas. 267 



differences if they mean anything, are more primitive fea- 

 tures than those of the types of Platypeltis and Psyloce- 

 phalus. 



Prof. Meneghini compares the species of these two Asa- 

 phus-like genera described by him, to species of the fauna of 

 Hof in Bavaria, of the Lower Tremadoc (Dolgelly) beds in 

 Wales and of the Upper Cambrian (Dictyonema) shales of 

 Shropshire. 



A type of Cambrian trilobites which one might expect to 

 find in Sardinia in association with genera of Dolgelly and 

 Tremadoc age, and which is represented in Wales and 

 Sweden, as well as in the western part of America, is 

 Dicellocephalus. This genus, which by the large size of 

 some of its species, hy its general form, and its mobile 

 pleura, represented at the close of the Cambrian age the 

 genus Paradoxides of its earlier time, is apparently un- 

 known in the Sardinian rocks. 



But Dicellocephalus had its precursor in a species of the 

 Paradoxides beds (Tessini sub-zone) in Conocephalites ornatus 

 described by Dr. Brogger from Krekling fA Norway. 



So many of the Tremadoc genera have their roots far 

 down in the Cambrian zones, that it seems impossible to 

 separate them from their relatives in the older beds. 

 Whether we look to the north of Europe, to Sardinia or to 

 the western United States of America, these links in the 

 chain of life seem too strong to be severed, and the Trema- 

 doc group should therefore be included in the Cambrian 

 system. 



If we desire a well defined line to separate the Cambrian 

 system from its successor this is afforded by the beds in 

 which the typical Arenig or Levis graptolites make their 

 appearance. 



One phase of the upper Cambrian fauna which we find 

 notably absent from the more . southerly regions where 

 Cambrian rocks are found, is the Peltura fauna. In Sweden 

 and Norway this presents quite a variety of small and 

 smooth or spinose forms related to Olenus, as it does also 

 in Wales, and to a lesser degree in Acadia, but from other 



