18 P. T. CLEVE, 



white marl. In this detrital mäss are found shells of terrestrial mollusca, some of which 

 are of extinct species and some no more extant in S:t Croix, but found living in the is- 

 land of Viéques and Puerto Rico. Among the former, that is the extinct species, are Helix 

 Santa cruz ensis Pfr, Bulimus extinctus Pfr, B. Riiseii Pfr, Pupa rudis Pfr, Cyclostoma basi- 

 carinatum Pfr, and C. chordiferum Pfr. Among the latter are Helix caracolla L., and H. 

 marginella Gm. 



In the detrital or alluvial beds, which cover the estates of Glynn and Concordia 

 around Salt-River, I have found many shells of Venus flexuosa Lin. and Ludna Jamaicen- 

 sis Spgl., species still abounding in the Caribbean Sea 



The recent marine formation is, in S:t Croix, as in most of the other West-Indian 

 islands, a calcarious sandstone, composed of small rounded pieces of shells, corals and cal- 

 carious algse, fixed together into tolerably firm and härd banks. In that limestone, often 

 employed as buildingstone, are imbedded shells of Turbo Pica L., Strombus Gigas L., and 

 other very common West-Indian shells; mostly with well preserved colours. 



IY. Leeward Islands. 



The islands north of Guadeloupe form two parallel chains from North-west to South- 

 east. The western chain commences with Saba and consists of S:t Eustatius, S:t Ritts, 

 Nevis, Redonda and Montserrat. All of those islands are volcanos and if the line were 

 extended farther to the north it would reach the island of Anegada, of postpliocene date 

 and all the volcanos seem to be of the same or nearly the same geological time. The Ba- 

 hama Islands, which are also most probably of postpliocene date, have the same direction 

 and seem to be the continuation of the same or of a parallel line of elevation. East of 

 the volcanic range is another completely different range of islands. They are not volcanic 

 and commence with Sombrero comprising Ånguilla, S:t Martin, S:t Bartholomew, Barbuda 

 and Åntigua. All of these islands are of the tertiary age, eocene, miocene and pliocene. 



Saba, a Dutch possession, is a small conical island rising abruptly from the surroun- 

 ding deep sea to the hight of 859 meters. The rock of the island is a more or less irre- 

 gularly stratified trachytic tufa, or in the eastern and north-eastern part trachytic lava 

 (microtinit), The trachyte has a reddish brown colour and contains white crystals of 

 glassy oligoklase and small black needles of hornblend. Near LTeWs Gate there occurs in 

 the tufa a sulphur deposit with gypsum and alum-stone. The sulphur isj evidently a rem- 

 nant of an old fumarol. I could not reach the highest point of the island, which is co- 

 vered by dense forests of arborescent ferns, but I do not believe that there is any crater, 

 the summit being terminated by a crest. From S:t Eustatius the island has the appea- 

 rance of a pointed cone, and from S:t Bartholomew the summit is terminated by a hori- 

 zontal line. The settlement rthe town of bottom» is a flat, almost circular space at the 

 hight of 2 — 300 meters above the sea, surrounded in all directions, by high steep hills of 

 tufa. To me it appears very probable that this is the true crater. 



