122 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Mar. 23, 



in some of the ancient bays in that neighbourhood (now a thousand 

 feet above the sea), a great variety and mixture of fossils are met 

 with in compact seams, very similar in condition and general ap- 

 pearance to the shells, &c. now thrown up in the bay of Monte 

 Christi, eighty miles distant, after a ground-sea. 



The district of Santiago is indeed of a very interesting character, 

 and rich in fossil remains. Between Fort St. Thomas* and the 

 junction of the River Cibao vdth the Yaqui is a high mountain-ridge, 

 called the Armasigo, along the crest of which may be traced, for 

 above two miles, a continuous Ime of coral, evidently the remains of 

 an old reef, which from its solidity has apparently served as a cap or 

 defence, and preserved this ridge from denuding forces until the sur- 

 face was fairly raised and out of danger. 



I may also observe, that on the River Amina the blue shale, 

 referred to as resting generally upon the sandstone and older rocks, 

 lies upon vmfossiliferous mottled clays. 



Notes upon the localities. 



Santiago (River Yaqui) . — Tertiary formation : beds of blue 

 shale,— dip S.E., Z 9° to 11°. 



Santiago is the capital of the Province of Santiago, it contains 

 about 5000 inhabitants, and stands upon a high bluif of the River 

 Yaqui. The bed of shale of which the bluff is chiefly composed is 

 compact and has a jointed structure. The partings run to the 

 S.S.E. andE.N.E. 



The River Yaqui springs from the northern flanks of the Cibao 

 Mountains ; its course is northward as far as Santiago, cutting its 

 way through the tertiary beds ; it here turns suddenly to the west- 

 ward, leaving a spacious platform (the site of the town) at an eleva- 

 tion of 1 .50 feet above the river. 



Fossils are not very abundant, being confined to a few narrow 

 seams, 5 or 6 inches thick, intercalated in the shale. These seams 

 are composed of shells, both entire and in a comminuted state, 

 mixed with fine sand, and have the appearance of a recent beach after 

 the efifects of a ground-swell from the ocean ; very similar to what 

 is seen in the Bay of Monte Christi occasionally at the present day. 



These beds suffered denudation to a certain extent after having 

 been tilted, and were subsequently overlaid by patches of coarse 

 shingle, the origin of which is not yet satisfactorily determined. 

 They cross the plain from the Cibao to the Monte Christi Range, 

 and gently thin oflP to the westward. They afi'ord a soil for the 

 purposes of agriculture only in low humid localities. The fertility 

 of the rich plantations to the east of Santiago is entirely due to a 

 subsequent argillaceous deposit which is highly retentive of moisture, 

 and is now covered by a deep vegetable mould. 



Nivaje. — This is the name of a deep narrow ravine, to the S.E. of 

 the town of Santiago, which exposes interesting sections of the blue 

 shale, &c. It affords mineral waters ; which spring from a bed of 



* The site of this fort was only lately discovered. It was the first military post 

 established in the interior, for the subjugation of the New World. Its position 

 and the track of Columbus from the coast are shown in the Map, fig. 1. 



