Geology. 305 



at the close of the Mesozoic Era was likewise precipitated by 

 external changes over which the mammals themselves had no con- 

 trol ; it bettered the condition of creatures who specialized in the 

 care of their young; and the use of their brains. Each group 

 which prospered had for some time displayed the very character- 

 istics which proved efficacious in the time of stress; the 'revolu- 

 tion' afforded the opportunity for the testing and the rewarding 

 of the products of progressive evolution. ... As in the past, so 

 in the twentieth century, the impelling forces of progress are 

 inherent in the environment; the response must be dependent 

 upon virtues intrinsic in the creatures who are to be thus tested. 

 Some will undoubtedly be found wanting ; for them the penalty 

 has always been either extinction or stagnation. Others — and in 

 the past it has generally been a minority — will respond with 

 habits that will prove to be their salvation ; they, and they alone, 

 will profit by the revolution. " c. s. 



2. Stratigraphy of the Pennsylvania!! Formations of North- 

 Central Texas; bv Frederick B. Plummer and Raymond C. 

 Moore. Univ. of Texas Bull. No. 2132. Pp. 237, 27 pis., 19 text 

 figs., 1921 (1922). — It is highly pleasing to note that this careful 

 and detailed work on the Pennsylvanian strata of north-central 

 Texas was done by the geologists of the Roxana Petroleum Com- 

 pany, and donated to science through the Texas Bureau of 

 Economic Geology and Technology. It is cooperation of this 

 kind that is to the advantage of humanity in practical and intel- 

 lectual ways. We congratulate all concerned. 



The maximum thickness of the Pennsylvanian here is about 

 6,800 feet, embracing the Bend, Strawn, Canyon, and Cisco 

 groups of formations. The report contains a large geologic map, 

 eleven photogravure plates of typical fossils, many other illustra- 

 tions, and a complete list of the known Texas Pennsylvanian 

 faunas, totalling about 354 forms. No new species are described. 

 Of cephalopods there are forty-three species and of these no fewer 

 than twenty-seven are goniatites and ammonites. c. s. 



3. Recent Mollusca of the Gulf of Mexico and Pleistocene and 

 Pliocene Species from the Gulf States. Part 2, Scaphopoda, Gas- 

 tropoda, Amphineura, Cephalopoda; by Carlotta J. Maury. 

 Bull. Amer. Paleontology, No. 38, 142 pp., 1922.— This is a list of 

 the Scaphopoda, Gastropoda, Amphineura, and Cephalopoda of 

 the regions and geologic times mentioned in the title. The bibli- 

 ography of each species is given, along with the distribution, and 

 there are also occasional notes on the forms. 



4. Handouch der Regionalen Geologic , 23. Heft, Aegypten, 

 by Max Blaxckexhorn; 24. Heft, Die Nordatlantischen Polar- 

 inseln, by Otto Nordenskjold. 1921. 



5. The Topographic and Geological Survey of Pennsylvania; 

 George H. Ashley, State Geologist. — The following bulletins, 



