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



the Grange Mountain, where the two deposits are very clearly 

 visible in the sea cliff. (See fig. 7, p. 126.) 



Fig. 4. — Transverse Section (No. 3) from near the junction of the 

 Rivers Taqui and Cibao, South of La Angostura, to the Palo 

 Quemado Mountain. Length about 9 miles. 



r. River Ravine of "• 



Gurabo. Nivaje. 3 2 1 



_______ _ River 



5 4 4 3* 4* 6 7 



1. Tufaceous limestone. "] 5. Red sandstone, — dip 25° S. by E. 



2. Shingle bed. 6. Conglomerates. 



3. ArgiUo-calcareous shales. Irr. »• /■ Dark flaggy sandstone and bituminous 

 3*. Do., modified. ?-^ertiary. shales,— dip 33° N.N.E. 



4. Blue shale. I 

 4*. Dark shale. J 



The lower beds, made up of these two shales, in some places 600 

 feet thick, are covered by a layer of shingle, consisting of pebbles of 

 many kinds of rocks, some of them 1 8 inches in diameter, and more 

 or less stained by oxide of iron. This conglomerate is of variable 

 thickness, from 1 to about 10 feet, and the surface of the shale on 

 which it reposes has in many places been eroded into cavities which 

 are filled by the conglomerate. Lastly, this shingly conglomerate 

 is covered by a tufaceous* limestone at least 300 feet in thickness. 

 (See Map, and figs. 5 & 6, p. 124.) 



The shales have a general dip of from 5° to 7° to the N.N.W., 



* Mr. H. C. Sorby, F.G.S., has most kindly supplied the following note: — The 

 term " tufaceous " applied to this limestone, on account of its quasi-vesicular and 

 roughly crystalline appearance, is inaccurate. The physical composition of the 

 coarser-grained specimen from the Grange is — 



Entire and fragmentary shells of a discoidal foraminifer 40*0 



Fragments of two or three species of corallines 12*0 



of coral 2'0 



Entire and fragmentary foraminiferae, of several species, smaller than 1 ,.- 



the above j 



Crystalline matter surrounding the above, no doubt chiefly derived "I .,.. 



from decayed coralUnes and foraminifera; j 



Empty cavities due to segregational removal 3"0 



Peroxide of iron -1 



loo^o 



The discoidal foramiuiferas above referred to are small, being from ^V^li to 

 gijth of an inch in diameter, and hence are not readily recognized until seen in a 

 thin section. Some of the fragments of corallines are quite rounded, so that, if 

 their structure were not attended to, they might be mistaken for oolitic grains. 

 There are no fragments which can be referred with certainty to the shells of mol- 

 lusca. What was no doubt originally fine granules of decayed corallines and 

 foraminiferae, surrounding the fragments, has become crystalline, but not of coarse 

 grain ; and during this process the empty cavities have been formed, which in 

 some parts are much more numerous than stated in the analysis ; and the structure 

 of some of the fragments has become obliterated. The finer-grained specimen 

 from the same locality is composed of much the same material in a more finely 

 comminuted state, and is imperfectly consolidated. Independent, therefore, of 

 any other facts than those revealed by the microscope, I should be led to consider 

 this limestone to be a marine deposit of a warm climate, in some respects analogous 

 to those now taking place near the West Indian coral reefs. [July 18, 1853.] 



