ON THE GEOLOGY OF THE NORTHEASTERN WEST-INDIA ISLANDS. 



13 



posing this islaucl are stratified, micaceous, and amphibolitic schists and beds of compact 

 felsite. The strata strike E. N. E. — W. S. W. and dip 70° southward. 



JUi Rnund Rock. 



J 

 Ginger I. 



jfl^fl Diorite. 

 : I I Slate and Flagstone. 



V HUl Granular Granite. 



•4;-- J g||§ Trappous Rock 



fn nej>T |;;j;jj;;| Recent calcarious sand. 



Saltj Hl Limestone. 



(Map of Salt Id. Cooper Id, Ginger Id and Round Rock). 



Peters Island. I have only visited the northern part of the island, but sailed very 

 near the southern part. The rocks on the north-eastern shore are micaceous and amphi- 

 bolitic schists, intersected by dikes of granular granite. The stratified rocks have a strike 

 E — W. and dip southward at a very high angle. The southern part of the island is a long 

 and narrow promontory, probably composed of felsite or granular granite. 



Normans Island, between Peters and S:t John, is a tolerably large islet of felsitic 

 rock, (quartz-porplryry and protogin-felsite). Near Normans Island there are some smaller 

 cays, as Pelicans Island and Flanagan Cay. 1 have not been ashore in any of them but 

 by their appearance from the sea one may judge them to be felsitic rocks. 



10. Anegada*), has about the same size as Tortola, but is in all respects different 

 from the other Virgin Islands. Its extent from N. W. to S. E. is about 17 kilometers. It 

 is very narrow, being scarcely more than 3^ kilometers broad. The surface is flat and 

 only 9 meters above the sea-level. All the shore of the island is a härd, compact lime- 

 stone with numerous fossils, which all belong to species still living in the Caribbean sea. 

 The fossils are well preserved, and in one specimen of Conus Leoninus Rewe the coloured 

 spöts were still visible. The fossil shells are all of shallow-water species. The most abun- 

 dant are Bulla striata Brug, Oliva reticularis Lk. Ludna pennsglvanica Lin etc. The lime- 

 stone is consequently of a very recent date, probably post-pliocene. The rock contains 

 many natural pits and caverns, at the bottom of which there is a mäss of soft black earth. 

 The island has many large and shallow lagoons with brackish water. On the northern coast 

 are large and hijjh masses of loose calcarious shells-and. 



11. Crab Island or Vieques, a Spanish possession near Puerto Rico, and south of 

 Culebra. It extends E — W. about 33 kilometers, and is not more than 7 kilom. in breadth 



*) The island of Anegada is described by R. H. Schombtjrgk in the Journal of the Geographical Society of 

 London. Vol. II 1832 p. 152. 



