454 SCIENCE PROGRESS 



and nepheline-basalts. Dr. Cross further destructively criti- 

 cises the unhappy " Atlantic-Pacific " classification of igneous 

 rocks, and the memoir contains much excellent petrological 

 discussion of a general character. 



A rare igneous type, bekinkinite, hitherto only known from 

 the type-locality of Bekinkina, Madagascar, has been discovered 

 at Barshaw, near Paisley, by officers of the Geological Survey 

 of Scotland. A further discussion of the occurrence is given 

 by the writer (Geol. Mag. 191 5 (6), 2, 304), who also records the 

 presence of another rare type, lugarite, as veins in the pre- 

 dominant bekinkinite. Both rocks are rich in nepheline and 

 analcite. 



Petrology-Sedimentary Rocks. — An investigation of the 

 chemical composition of the skeletons of present-day crinoids 

 and echinoderms by F. W. Clarke and W. C. Wheeler (United 

 States Geological Survey, 191 5, Professional Papers, 90-D and 

 90-L) has disclosed the novel and important facts that the hard 

 parts of these animals are comparatively rich in magnesium 

 carbonate (6-14 per cent.) ; and that the proportion of this 

 constituent varies with the temperature of the water in which 

 the organisms thrive. On the other hand fossil crinoids are 

 much poorer in magnesium carbonate (average if per cent.). 

 With further work it is probable that these facts will be found 

 to have an important bearing on the origin of magnesian and 

 other limestones. W. H. Twenhofel (Amer. Jour. Sci. 191 5, 

 40, 272) describes a black shale at present forming in swamp 

 waters on the Esthonian coast of the Baltic Sea. From this 

 occurrence he concludes that black hydrocarbonaceous shale 

 may form in water so shallow that it is but a step to land con- 

 ditions. A review of theories of black shale formation leads him 

 to the conclusion that marine and non-marine types may be 

 differentiated and that this kind of deposit is by no means 

 generally indicative of deep-water conditions. 



In an account of geological exploration along the Canadian 

 Pacific Railway from Golden to Kamloops, British Columbia 

 (Geological Survey of Canada, 191 5, Mem. 68), Prof. R. A. Daly 

 describes interesting dune-sand quartzites and quartzite of 

 loess-like character in the Beltian System (Pre-Cambrian) of 

 that part of the North American Cordillera. The former con- 

 sist of minute, perfectly rounded quartz grains ; the latter are 

 distinguished by their very fine-grained, homogeneous, thick- 



