502 abstracts: geology 



formation of the Coosa Valley and adjoining areas shall be restricted 

 to the Upper Cambrian, and the Middle Cambrian beds there given a 

 formation name, is left for further detailed study. 



The discussion and comparison of the Crepicephalus group of trilo- 

 bites is particularly interesting, including a comparison of 17 different 

 species, 10 of them new species, 3 new varieties, and two undetermined 

 species. The five plates of illustrations of this large trilobite also 

 present many new and interesting features of the animal, now so long 

 extinct. G. R. B. 



GEOLOGY. — The Caddo oil and gas field, Louisiana and Texas. George 



C. Matson. U. S. Geologicl Survey Bulletin 619. Pp. 62, with 



map, sections, and illustrations. 1916. 



This bulletin contains a description of the physiography, geology of 



the Cretaceous, Tertiary, and Quaternary systems, and the structure 



of the rocks in the Caddo oil and gas field. It also discusses relations 



of oil and gas and the possible extensions of the Caddo oil field. 



R. W. S. 



GEOLOGY. — Ground water in San Joaquin Valley, California. W. C. 

 Mendenhall, R. B. Dole, and Herman Stabler. U. S. Geologi- 

 cal Survey Water-Supply Paper No. 398. Pp. 310, 5 plates and 

 4 figures. 1916. 

 This report outlines the geography and geology of the valley, the 

 character of the soils, and the availability of the surface waters, and 

 describes in detail the occurrence, utilization, and quality of the ground 

 waters, especially in reference to their availability for irrigation, boiler 

 supply, and domestic use. The great value of the agricultural products 

 and the lack of sufficient surface water in this valley have brought 

 about unusual development of ground water resources. Nearly every 

 phase of practical irrigation is illustrated, including flood, deep-ditch, 

 and subterranean irrigation, the utilization of deep waters, the use of 

 steam and gas engines and electric motors for power, the disastrous 

 rise of alkali, the effect of alkali on growing plants, and the applica- 

 tion of strongly mineralized waters. Ground water of good quality 

 can be pumped at moderate expense throughout the east side of the 

 valley, but the level of the ground water on the west side is much 

 deeper and the mineral content of the water is much greater; yet neither 

 its cost nor its quality will prevent its ultimate use in many parts of 



