154 DR. THOMAS STERRY HUNT ON THE 



some twenty years since by Messrs "Wall and Sawkins/' by whom they were designated 

 as the Caribbean gronp, more recently by Mr. R. J. Lechmere Gruppy, and in 18*78 were 

 examined by Crosby. 



§ 205. The strnctirre of the Northern Mountains in Trinidad is monoclinal, high 

 Bontherly dips being iiniA'ersal. The thickness of the strata exposed is not less than 

 10,000 feet, included in three divisions : a lower consisting of a qnartzite, granular and 

 usually more or less micaceous, followed by and alternating with hydrous micaceous 

 schists and argillites, often lustrous ; a middle one of several thousand feet of crystalline 

 limestones in massive beds, varying in colour from white to nearly black, and often some- 

 what micaceous ; and an upper division consisting of several alternations of argillites like 

 those of the first, frequently graphitic, and often passing into hydromicaceous schists, with' 

 layers of quartzite, sometimes detrital, and, towards the summit, thin beds of limestone. 

 The whole succession, according to Crosby, strongly resembles the Taconian as seen in 

 western Massachusetts. Overlying unconformably this ancient series, which appears to 

 be unfossiliferovrs, is a dark-colored compact fossiliferous limestone, with interbedded 

 shales, in which, among many obscure forms, Guppy recognized Murchisonia Anna and M. 

 linearis, both found in the Calciferous sand-rock in Canada. 



§ 206. Subsequent observations of Crosby," in 1882, made in the mountains of eastern 

 Cuba, between Baracoa and the southern coast, show that there exists to the south of the 

 diA'iding ridge a belt six or eight miles wide of highly inclined strata, having an east and 

 west strike, and consisting of hj'dromicaceous and chloritic schists with immense beds of 

 white crystalline limestone, often micaceous. This group is entirely distinct from one 

 made up from fissile slates, soft sandstones and impure earthy limestones, found chiefly on 

 the northern slope of the same mountains, and regarded by him as probably equivalent to 

 the cretaceous and tertiary strata of San Domingo and Jamaica. Of the first named group 

 he says : " These rocks bear a strong resemblance to the Taconian system of western New 

 England, and are essentially identical with the great series of semi-crystalline schists and 

 limestones of Trinidad and the Spanish Main, which I have elsewhere correlated with the 

 Taconian." From the published accounts of the geology of San Domingo and Jamaica, 

 Crosby conceives that these islands have a similar structure to that of south-eastern Cuba. 

 Their crystalline schists which, according to him, have been generally confounded with 

 the cretaceous beds, he believes to be like those of Cuba, and of Taconian age. Cleve, in 

 18*70, noticed in Porto Eico, Santa Cruz and the Virgin Islands an unfossiliferous series 

 which he conjectured might be metamorphosed cretaceous. These strata, which are verti- 

 cal, or have a high northern inclination, consist chiefly of argillites and crystalline lime- 

 stones like those of Ci^ba and Trinidad. ^^ 



§ 20*7. There exists in the Alps, besides the ancient or central granitoid gneiss 

 (Laurentiau), the great pieire verdi series proper (Huronian) and the younger gneiss and 

 mica-schist series (Moutalban), a fourth great group, very widely distributed, made up in 



*' Wall, Geology of Trinidad, etc., 18G0, Quar. Geol. Jour, xvi, 660. 



*^ W. O. Crosby on the Probable Occurrence of the Taconian in Cuba ; Science, December 7, 1883, p. 740 ; also 

 in abstract in Eeport of Smithsonian Inst, for 1883. 



*" P. T. Cleve, Kongl. Svenska Veten.sk.aiis-Akademiens Ilanillingar ; P.andet 9, No. 12. Tlie cretaceous age of 

 the crystalline schists and limestones of San Domingo was maintained by Gabb in his memoir on the Topography 

 and Geology of the Island, etc., in 1873 ; Trans. Amer. Philos. Soc, vol. xv. 



