1853.] HENEKEN — SAN DOMINGO. 123 



sandstone, exposed by the deep cutting of the ravine. A few fossils 

 were here collected bearing the usual character. 



The large Ostrea Virginica is here abundant, and, from the pre- 

 valence of fossil wood in detached masses, this locality seems to have 

 once formed a small bay or the estuary of a river. The wood is met 

 with in different stages of carbonization, much of it is permeated by 

 sulphate of lime, and some pieces are entirely riddled by Teredines. 

 The strata along the ravine are much disturbed. 



Las Charcas. — Beds of blue shale : dip N.E. by E., Z 7°. 



Ascending the River Yaqui from Santiago to the southward, at 

 the distance of three or four miles over the blue shale, is the Farm 

 of Las Charcas. 



The cliifs of the river are full as high here as at Santiago, but they 

 are richer in fossils, and the same fossiliferous seams prevail. 



The upper parts appear to ha^e been denuded, and afterwards 

 covered with coarse shingle, and at a still later period a yellowish 

 marl was deposited on the latter. 



The shale here, as at Santiago, assumes a jointed structure; the pre- 

 vailing direction of thepartings is S.E. byS.,E. by S., andS.W.by W. 



Hills of Samba (eastern extremity) . — This range of hills crosses 

 the River Yaqui a short distance south of Las Charcas, the river 

 being confined to a very narrow passage between perpendicular walls 

 of a hard calcareous rock in alternate seams with a soft ferruginous 

 sandy shale, dipping north Z 23°. These seams appear to be 

 modifications of similar strata noticed at Cercado, and of an argillo- 

 calcareous shale that comes out at the Grange, — a band that follows 

 the Samba Hills throughout their whole course. 



Impure ferruginous sandy calcareous shale of much the same 

 nature covers these seams vdth a dip N. byW. Z 10° to 14° It is 

 traversed by perpendicular joints, running N. and E.S.E. The hill 

 is covered by tabular masses of tufaceous limestone. 



La Angostura. — Black and yellow shales, — dip N.E. Z 7°. 



This place appears to have once formed a deep bay or corner of 

 the tertiary basin. The cliffs of the Yaqui continue to have an 

 average height of above 150 feet, but the component materials are 

 somewhat modified, being formed of a soft blackish shale, in some 

 places almost composed of fine black sand. This bed contains fossils, 

 both disseminated and in thin indurated seams. The shale is also 

 more or less mixed with gravel in the upper parts, and is covered by 

 the soft yellow sandy calcareous shale of Samba, also fossiliferous; 

 but the fossils, as is usual in all ferruginous strata, are in a bad state 

 of preservation. The bed of yellow shale here is about 50 feet thick. 

 Corals are small and rare. 



Beyond Angostura, and at the mouth of the River Cibao where 

 it joins the Yaqui, the tertiary beds are in contact with secondary 

 rocks (perhaps of the Carboniferous system), which consist of dark 

 sandstone flags, alternating vdth black bituminous shales in narrow 

 seams, dip N.N.E. Z33°. No fossils were observed. 



Postrero (River Amina). — Beds of blue shale, — dip N.W. by 

 N. Z 5°. 



VOL. IX. — PART I. K 



