Reviews — Les Echinides des " Bagh Beds ". 229 



" Hypersthene Syenite and Related Rocks of the Blue Ridge Region, 



Virginia," by T. L. Watson and J. H. Cline. Bull. Geol. Soc. 



Amer., vol. xxvii, pp. 193-234, 1916. 



This petrographic province, -which is probably of pre-Cambrian 



age, comprises a batholith about 150 miles long by 20 miles wide, 



composed of differentiates of a syenitic magma; the chief types are 



quartz-hypersthene syenite, granite, norite, gabbro, pyroxenite, and 



a quartz-felspar-epidote rock. 



"Zircon-bearing Pegmatites in Virginia," by T. L. Watson. Trans. 

 Amer. Inst. Min. Eng., vol. lv, pp. 936-42, 1917. 

 Pegmatites from Amelia County contain zircon, with beryl, helvite, 

 allanite, columbite, and monazite, while those from Hanover County 

 are specially characterized by zircon and rutile. 



" The Emerald Deposits of Muzo, Colombia," by J. E. Pogue. Trans. 

 Amer. Inst. Min. Eng., vol. lv, pp. 910-34, 1917. 

 A detailed description of the emerald deposits and their associated 

 minerals with an account of the present state of the mining industry. 

 The origin of the emeralds is ascribed to mineralization associated 

 with intrusion of pegmatites. 



EEVIEWS. 



I. — Les Echinides des "Bagh Beds". By R. Eouktau. Records 

 Geol. Surv. India, vol. xlix, pt. i, pp. 34-53, pis. i, ii, 1918. 



rpHE age of the marine Cretaceous series of the lower part of the 

 JL Narbada Valley, generally known as the Bagh Beds, has long 

 been regarded as Cenomanian, a view based to a large extent on 

 Duncan's researches on the Echinoids. Other views of their age 

 have been expressed, notably those of Stoliczka and of Bose, who 

 both considered that more than one Cretaceous horizon was 

 represented. At the time of Duncan's writing the Echinoids were 

 the only group of fossils from these beds that had been critically 

 examined, but Mr. E. W. Vredenburg has since studied the 

 Ammonites, although he found that they did not help in determining 

 the exact age of the beds. 



The specimens upon which Duncan based his conclusions have 

 lately been re-studied by M. R. Pourtau, whose results are valuable 

 because they determine more accurately the relationships of these 

 Echinoids, and also fix the age of the beds with more certainty. 

 Duncan was so convinced by the general facies of the Echinoids that 

 he was dealing with an undoubted Cenomanian fauna, that he did not 

 find it necessary to make comparisons with older forms. M. Fourtau, on 

 the other hand, was much puzzled by the record of two of the 

 species, Salenia fraasi and EcJiinobrinus goyheti, since they belong 

 to an horizon which R. P. Zumoffen has recently shown to be 

 synchronous with the Aptian of the Mediterranean border. He has 

 therefore made comparisons with a wide range of species in the 

 Cretaceous, and he concludes that the Echinoids have affinities with 

 the Early and Middle Cretaceous forms, that the Bagh Beds are of 



