Geology. 337 



nated in the oldest Lower Cambrian, " or at a still earlier period," 

 in a stock ancestral to both (p. 92). 



The author further differs with Walcott, holding that the 

 Olenellus zone of the Lower Cambrian probably does not overlie 

 the Callavia zone. Rather that both are practically of one time 

 but of two basins. The proof for this he sees especially in that 

 " a profile has never been found in North America in which an 

 Olenellus zone succeeds above a Callavia zone" (109). 



Kiser also discusses the probability that the unfossiliferous, 

 widely extended, and thick Sparagmite formation of central 

 Scandinavia is a continental deposit, and that instead of its being 

 of latest Proterozoic age it is more likely of earliest Low^er Qam- 

 brian time. His interpretation of the succession is as follows : 



Upper jjart of Lower Cambrian. Marine. About 50 meters thick 



Zone of Strenuella llnnarssoni 



Zone of Holmia kjerulfi ^ Equivalent to Callavia 



Zone of Discinella holsti ! time in the Atlantic province 



Sandy shales with trails and (of North America 

 Torallella J 



Middle and lower part of Lower Cambrian. Sparagmite forma- 

 tion. Continental deposits. Very thick. 



Kieer holds that the Strenuella zone passes unbroken from the 

 Lower into the Middle Cambrian (99), and refers it to the former 

 division even though no Mesonacidge occur here. He does this 

 because it has a few species, other than trilobites, of the older 

 horizons, none of which, however, appear to the reviewer to be of 

 straiigraphic value. The author admits the great difficulties 

 here, but seems to give little value to his conclusions that the 

 earlier faunas invaded Scandinavia from the opposite direction to 

 that of the Strenuella assemblage. In other words, that the paleo- 

 geographies of these times were markedly different. He also 

 plainly shows that the Middle Cambrian sea is an overlapping 

 sea across an irregular topography, and further, that the terminal 

 Lower Cambrian Protolenus zone of the Atlantic realm is absent 

 in Scandinavia. For the present the reviewer would therefore 

 rather believe that the Strenuella zone is of Middle Cambrian 

 age and of Atlantic faunal affinities. Further, that the Lower 

 Cambrian is separated from the Middle Cambrian by a time break 

 of considerable magnitude, during which time there was enough 

 warping of the land to bring about wholly different sea invasions. 



c. s. 



4. Recurrent tetrahedral deformations and intercontinental 

 torsions ; by B. K. Emerson. Proc. Amer. Philos. Soc, Ivi, pp. 

 445-472, 1917.— This is a very interesting article, and should be 

 read in connection with the author's presidential address before 

 the Geological Society of America, printed in volume 1 1 of the 

 Bulletin of that society under the title " The tetrahedral earth 

 and zone of the intercontinental seas." c. s. 



5. On the crinoid genus Scyphocrinus and its bulbous root 

 Camar.ocrinus; by Frank Springer. Smithsonian Institution, 



