324 Notices of Memoirs. 



Jimbo as long ago as 1896 in the Journal of the Tokyo Geographical 

 Society, vol. viii. The specimens, of which there are two, can only 

 be distinguished from * A. tuberculosa, Linn.' (said by Yoshiwara 

 to be identical with A. nodosa, Sol., and A. oryzata, Mensh.), by 

 the general outline of the shell, the size of the whorls near the 

 centre, and the rows and numbers of the ribs. It is of considerable 

 interest to find that this tuberculate form of the genus, which has 

 never been found living in Japan, existed there in Tertiary times. 



VI. — The Grand Canyon of the Colorado. — Professor W. M. 

 Davis has published in the Bulletin of the Museum of Comparative 

 Zoology at Harvard College (Geol. Series, v, No. 4, May, 1901) an 

 account of an excursion to the Grand Canyon of the Colorado. His 

 results maybe summarized as follows : — "There is some probability 

 that the San Kafael swell, like the Waterpocket flexure, is of 

 pre-Tertiary origin. The other deformations of the region, both 

 flexures and faults, are almost exclusively of much earlier date than 

 the canyon cycle, and they may have been formed relatively early 

 in the erosional history of the district. The total denudation of 

 the region thus far accomplished may be considered in two parts, 

 of which the first — the great denudation — was far advanced before 

 the general uplift by which the second — the erosion of the canyon 

 and the stripping of weak strata from the plateaus — was introduced." 



" But the great denudation was complicated by repeated move- 

 ments, after each of which the processes of erosion may have 

 reached an advanced stage before the occurrence of the next series 

 of disturbances. It is only by an analysis of these repeated 

 movements and revived erosions that the origin of the drainage 

 system can be determined. As far as this analysis can be attempted 

 at present for the Grand Canyon district, the side streams seem to 

 be of various origins, except that none of them appear to be 

 antecedent. The Colorado itself may be in part antecedent to some 

 of the many dislocations that the district has sufi"ered, but it seems 

 to be for the most part consequent on the displacements caused by 

 faulting in the later part of the great denudation, and on the form 

 that the surface had assumed at that time." 



" The floor of the Toroweap valley is higher than the neighbouring 

 valley floors, because it is sheeted with heavy lava flows which have 

 effectively withstood the intermittent erosive effects of wet-weather 

 floods. The past climate of the region cannot be safely determined ; 

 a change from a humid to an arid climate at the close of the Miocene 

 does not appear to be demanded by the facts that have been appealed 

 to in its support." 



Professor Davis gives a bibliography and some illustrations, many 

 of which are new, and one of which, a general photographic view of 

 the Grand Canyon, is especially good. T. E. J. 



VII. — Shorter Geological Notes. — Elkanah Billings, for 

 twenty years palEeontologist to the Geological Survey of Canada, 

 and the founder of the Canadian Naturalist and Geologist, formed 

 the subject of Dr. Ami's address as president of the Ottawa Field 



