28 Reviews — Spencer s Cretaceous Starfishes. 



but the effects of eartli-moveraents on tlie shapes of valleys, as 

 indicated by 'Professor J. W. Gregory in his work on fiords (see 

 Geol. Mag., December, 1913), has not always been sufficiently 

 considered. How greatly disturbances have influenced the physical 

 features is shown in the present volume in some of the sections of 

 the Yosges, Alps, Western Jura, and Uinta Mountains. 



There are grand views of mountain peaks and others showing the 

 influence of weathering agents on different rocks, as in the Dolomite 

 mountains ; the influence of joints, columnar, tabular, etc. ; of sills 

 and laccoliths, batholiths or bosses, as in the Skye plateaus and 

 mountains, the latter generally known as the Cuillin and lied mils. 



One chapter is devoted to an account of the leading geological 

 phenomena of the Pacific Ocean and its coast-lands, and the author 

 expresses his opinion that " Although it is not possible to demonstrate 

 that the Pacific Ocean is of primeval antiquity, yet all the phenomena 

 seem to favour that conclusion, and to negative the idea of a great 

 Pacific continent such as the geosynclinal theory desiderates ". 



The Subsequent or Relict mountains include those carved out of 

 plateaus of accumulation, such as the basalt plateaus of the Inner 

 Hebrides, the heights of Saxon Switzerland, the tabular mountains 

 of North African deserts, the Buttes of Wyoming, and the Bad Lands 

 of Nebraska, as well as other escarpment heights and the features 

 connected with canons. It is admitted that some laccolith heights 

 and many volcanic 'necks' must be regarded as Relict mountains, 

 but, as the author observes, it is usually difficult, when dealing with 

 Nature, to draw hard and fast lines. 



lY. — The Evolution of the Ceetaceous Asteeoidea. By W. K. 

 Spencee, B.A., F.G.S. Phil. Trans. Rov. Soc, ser. B, vol. 204, 

 No. 306, pp. 99-177, pis. 10-16, 1913. " 



THE work of Mr. W. K. Spencer on the Cretaceous Asteroidea, 

 published during the last few years in the volumes of the 

 Palaeontographical Soeietj^ has been done chiefly from the systematic 

 point of view. Much light has been thrown on the subject by his 

 philosophic treatment in the present paper of the evolution of the 

 group. A clear and useful summary of the aims of the essay serves 

 as an introduction to the author's results, which are arranged under 

 three headings, dealing respectively with the description of the 

 ' species series ', stratigraphical conclusions, and variation and 

 evolution. Eight new genera and one new subgenus are established, 

 and the classification adopted is that of Perrier. 



The Cretaceous rocks not only of England but also of many 

 important Continental districts have been considered, and from the 

 stratigraphical point of view the results are satisfactory. The author 

 finds that the Asteroid fauna could be used as a basis of horizonal 

 classification, and that isolated ossicles are of value for zonal 

 purposes. In the Upper Chalk of England the distribution of the 

 Asteroids shows the zoological break at the top of the lower third of 

 the coranguimim zone that was observed by Dr. Rowe in the case of 

 the Echinoids. For this reason, as Mr. Spencer thinks, it would be 



