HILL: GEOLOGY OF JAMAICA. 105 
In addition to the true islets there is a circular head projecting from 
the land as a peninsula, the narrow neck of which, if severed, would 
leave an islet of the kind we have described. This and the land im- 
mediately back of the island is a mangrove covered morass of the type 
Wwe have just described as the Montego formation. 
Nowhere can so grand a combination of erosive and constructional 
Processes or the successive formations of the Coastal Series, as a whole, 
and their relations to the older formations of the island, be seen in a 
Single view as at Montego Bay. This is a great indentation into the 
Coast, the back country of which is composed of beautiful hills covered 
With tropical upland vegetation, rising in a series of grand terraces to 
a height of 1,000 feet or more, as shown in Figure 6 and on Plate XX. 
This plain is composed of the following formations of the Coastal 
Series: the Manchioneal beds, the twenty-five foot level or middle old 
reef, tho low level Soboruco, and the Montego formation, while the 
Bogue Island formation barely appears abovo the waters of the bay. 
In the shallow bay fringing reefs are growing, and Mollusks, Echinoderms, 
and other sea shells are dying and contributing shell débris, which near 
the shore is mingling with the aggradational alluvium brought down 
by the rivers. Elsewhere it forms great deposits of purest calcareous 
Sand, 
The Montpelier formation, with its contorted beds of chalk and flints, 
forms the back coast hills in which this scene is set, and against which 
the various other formations lie in unconformable contact. Fragments 
of the yellow marls allied to the Manchioneal formation can be seen 
Against this on the west point of the harbor between the mouth of 
Great River and Round Hill Point. The old Soboruco, now converted 
‘ito a white limestone rising fifty feet or more, constitutes the opposing 
Northeast point of the bay. The railway station back of the town is 
“pon a low level plain made up of shell bearing marls equivalent to the 
"almouth formation, while the low coast Soboruco borders the sea at 
the city and Round Hill Point. The Montego formation occupies a still 
Ower plain, almost or at sea level, cut out of the low Soboruco and 
Falmouth formation, as seen in the morasses south of the city, The 
“identation comprising the bay and coastal plain was eut by the com- 
bined forces of erosion baselevelling the land, and wave action indent- 
Mg the shore, probably in late Pliocene time ; afterwards this plain was 
Submerged, veneered by deposited sediment from the land, and inhabited 
Y growing reefs. Later elevation brought the interior margin of the 
AY above the water, constituting the present low land extending be- 
