14 



from N — S. I did not remain in Crab Island more than a few days, and under very un- 

 favourable circumstances, for which reason I do not know much about the geology of the 

 island. Near the shore of Puerto Mula an altered dark green rock is visible, but at a 

 short distance from the coast occurs syenite-like diorite, which seems to be the most im- 

 portant rock of the island, producing by alteration a very fertile soil. The diorite has 

 the same appearance as the rock of Virgin Gorda, and has also a spheroidal structure. 

 In the eastern part of the island some stratified white rock seems to occur, but having 

 seem them only from the sea, at a considerable distance, I cannot give any description 

 of them. 



II. Puerto Eico. 



In this large and beautiful island I unfortunately passed too short a time, and in 

 an almost insupportable heat, so that I have not been able to get more than a very in- 

 complete acquaintance with its geology. I have visited the northern coast-line from the 

 capital S:t Juan to Quebradillas and in the interiör the mountains around Utuado. 



Near the northern coast the island is a hilly land, gradually rising in the interiör 

 to mountains of a considerable height. The hills along the coast are fragments of a very 

 thick series of strata, which have been cut through by rivulets andjoy denudation. The strata 

 are very little inclined, and the dip, from the axis of the island to the sea, is only a few 

 degrees. In the high mountains I have seen the summits still covered by limestone formation. 

 The bottom of the valleys between the hills are generally covered by detritus and a reddish 

 clay containing shells of still living, species as Helix caracoila L. B. marginella Gm and 

 Megalostoma cylindraceum. Chemn etc. Near the capital the limestone-rock is soft and I 

 have found there some fossil claws of crabs and casts of bivalves. In most other places 

 the limestone is a yellowish white and very härd rock. It contains fossils in the form 

 of casts or impressions. 



Near Quebradillas I made a little collection of fossils, but not having had time for 

 a careful determination of them, I can for the present only say concerning them, that some 

 of the fossil shells belong to species still living in the Caribbean Sea, as Latirus infundibu- 

 lum Gm., Area squamosa Lmk, Cancellaria reticulata Lin, and some belong to species found 

 in a fossil slate in Cuba, as Venus cariba?a d'Orb and Tellina Gruneri, Say (Tellina Sagros 

 d'Orb), the latter of which is still living in the West-Indies, though very rare. Some are 

 found in the miocene beds of Jamaica, as Pleurotoma Barettii Guppy, Phos Moorei Guppy, 

 Cancellaria la?vescens Guppy, Malea Camura Guppy, and Venus Woodwardii Guppy. Very 

 comrnon is a species of Bulla, which I believe is identical with B. granosa Sow from the 

 miocene beds of S:t Domingo. I have also found some fossils, which occur in the miocene 

 beds of Anguilla, as a species of Thracia and the calcarious tubes of a large Teredo. 

 There can be no doubt then that the age of the rock is the miocene. Below that forma- 

 tion occurs an older one, visible in the mountainons part of the interiör, and where rivers 

 have cut through the limestone-rock. That formation consists of conglomerates resembling 

 bluebeache, felsite and metamorphie stratified rocks, very similar to the rocks of the Virgin 



