OF SAXTO nOMINOC). 



the summit I found, in a bed somewhat more calcareous tlian the others, Sei^taria 

 and corals very similar in their mode of occun-ence to that of tlie same species near 

 Guayubin. 



J^oi th of Moca no other rock exposures occur. The valley is flat to the base of the 

 hills, and the black soil makes this vicinity one of the most productive agricultural 

 districts on the Island. The region east of Moca and Vega is equally uninteresting 

 to the geologist. A broad plain runs east between the two ranges of hills ; the river 

 bottom is a sheet of black alluvial soil of almost incredible fertility, while near the 

 hills the gi'avel and sand w^ashed down from their sides makes a porous soil which only 

 supports grass and which is thus admirably fitted for cattle-raising. The sluggish 

 Yuna winds its way through the middle of the valley, its banks, mud blutFs, support- 

 ing an almost unbroken forest, while its more lively tributaries, the Camu and the 

 Jima, as well as the upper part of its own course, hurry between the banks of shingle 

 brought down from the mountains of the far interior. But a single exception to this 

 monotony exists. Near the mouth of the Camu, on the south side of the Yuna above 

 Platanales, I found a single outcrop of white limestone in the side of the river bed. 

 It is partly under the water, partlj^ in the blutis, and is very similar lithologically to 

 some of tlie Miocene limestone of Samana. It is Miocene, and is the most northern 

 point at wdiich the Cevico belt crops out. Doubtless the same rock would be found 

 to underlie a great part of the valley if excavations were made. 



The eastern end of the valley for a dozen miles from the mouth of the river is ;i 

 tract of marsh. Part of it is almost constantly overflowed, while the more western 

 portion is grass-covered and drj , except in cases of extraordinai'y freshets or remark- 

 ably high tides, when it is temporarily covered with water. It is intersected by in- 

 numerable creeks which divide with the principal mouth the task of discharging the 

 waters of the river into Samana Bay. The bay is simply the prolongation of the 

 valley, and the marsh is now in process of being elevated into permanent dry land. 

 The Gran Estero which separates Samana from the main-land was a century ago a 

 navigable channel, but is now entirely closed. It is said to have been closed by 

 drift and mud from the Yuna. May not this elevation, which we have every reason 

 to believe is yet going on, have something to do with the obstruction ? 



A. P. s. — vor.. \'v. -?o. 



