Notices of Memoirs. 371 



still waiting to be filled in and branches of the subject still to be 

 investigated, but it is believed that they will produce no evidence 

 which will contradict the main results here worked out. The 

 division of the physical history of the region since Cretaceous times 

 into six stages or cycles is based on geological evidence which is 

 practically incontrovertible ; the assumptions as to the original 

 slope of the surface and the deformation of the peneplain are 

 supported by orographical measurements and geotectonic considera- 

 tions of great weight, as well as by being in harmony with evidence 

 from other parts of England; and, finally, the theory of consequent 

 and subsequent streams has been established on a firm foundation 

 by Davis and many other workers in the same field. The hypothesis 

 of the secondai-y origin of the IMoorland anticlinal as a watershed 

 more or less parallel to the original consequent streams has been 

 found to afford a natural and satisfactory explanation of the beliaviour 

 and characters of the watercourses which it concerns ; and the 

 modifications eS'ected by the Glacial Period have been interpreted 

 in most cases from direct field-evidence." 



II. — EocKY Mountain Eegion of Canada. — One of the last 

 labours of the lamented geologist, George Mercer Dawson, was 

 his presidential address, delivered before the Geological Society 

 of America on December 29th, 1900. It appeared in the Bulletin 

 for February. Dr. Dawson took as his text " The Geological Record 

 of the Rocky Mountain Region of Canada." The address was an 

 enumeration of the several formations now known to be represented, 

 a brief description of each, and a review of the main outlines of the 

 geological evolution of the area in so far as it has been made 

 apparent. Dr. Dawson began by giving a sketch of the physio- 

 graphical features, then he took the various formations in review, 

 and finally gave an excellent account of the physical history of 

 the area. 



III. — Age of the Earth. — Professor Joly's paper on the Age of 

 the Earth, discussed by Osmond Fisher in the Geological Magazine 

 for March, 1900, recalled to the memory of M. P. Rudzki a method 

 of estimation which he had published in Petermann's Mittheilungen 

 in 1895. Rudzki has now published his further researches and 

 results in Bull. Ac. Sci. Cracovie (February, 1901). The paper is 

 printed in French, 



IV. — A Fossil Crab and other Trails. — Cancer proavitus, 

 a new crab from the Miocene greensaud of Martha's Vineyard, is 

 described by Packard in Proc. Amer. Ac. Sci., 1900. It resembles 

 the living irroratus, and provides material for some general remarks 

 on the phylogeny of the genus Cancer. In another paper in the 

 same Proceedings Mr. Packard describes supposed Merostomatous 

 and other Palaeozoic arthropod trails, with some notes on those of 

 Limulns. He shows that there is a marked difference between 

 the trails of limuloids and isopods, and that while the trail of 

 Merostomichnites Beecheri is limuloid, that of Merostomichnites Narra- 

 gansettensts is isopodal. 



