Major A. J. Peile — N'otes on the Bermuda Islands. 418 



V. — Notes on the Geology of the BEEMtrDA Islands. 

 By Major A. J. Peile, E.A. 



I. 



IN a very interesting article on the Geology of Bermuda, published 

 in this Magazine for September and October, 1911 (pp. 385-95 

 and 433-42, Pis. XVIII-XXIII), the late llev. E. Ashington Bullen 

 states, on p. 390, that Admiral's Cave at Spanish Point is in the 

 Walsinghtim Formation. This statement is evidently due to a slip 

 in map-reading, Admiralty Cove being the boat harbour of Admiralty 

 House near Spanish Point, whereas the Admiral's Cave, whence the 

 Fcecilozonites nelsoni in the British Museum were derived, is the 

 " cave near the calabash-tree " mentioned on p. 439. This cave owes 

 its name to the visit of Admiral Milne, and the base of his stalagmite 

 is still in evidence, bearing his tool marks. It is one of the largest 

 and most remarkable of the many caves between Bailey's Bay and 

 Tuckerstown. 



With regard to the connexion between these shells and the formation 

 in which they occur, P. nehoni is found in great quantity, associated 

 with a few other species, in a bed of earth far within the cave. It is 

 probable that the earth was washed into the cave through some 

 hssure when the rainfall in the islands was greater than it is at 

 present. It is, however, noteworthy that the shells, which are well 

 coated with a stalagmitic (?) deposit, do not as a rule contain earth. 

 Traces of animal matter have been found in the inner whorls of some 

 of them, and broken specimens often exhibit colour-bands resembling 

 those of the living, but much smaller, P. hermudensis and its extinct 

 variety, P. zo7iatus. In fact, the circumstances under which they are 

 found here and in other caves ^ make it unlikely that the shells are 

 contemporaneous with the rocks in which the caves are formed. 

 P. nelsoni is also to be found in hard rock, and so are other species, 

 some of which are extinct. In many cases the shells had evidently 

 found their way into crannies in the rock, where they were later 

 cemented in by stalagmitic deposits {vide diagram, p. 390). In other 

 cases they appear to be regularly embedded in the mass of the 

 limestone. It is probable that the variations in character of the 

 seolian sandstone, due to chemical deposits from infiltered water, are 

 not always an index of the age of the rock, so that it is just possible 

 that the presence of these shells does not definitely determine a 

 deposit as belonging to the Walsingham Formation, as suggested on 

 p. 390. 



It is interesting to note that the small neck of land between 

 Castle Harbour and Harrington Sound, which is honeycombed witli 

 caves containing fossil shells, and which differs somewhat in the 

 character of its vegetation from the rest of the islands,^ is perhaps 

 the only present habitat of two of the species of endemic snails tliat 

 flourished along with P. nelsoni. These are P. reinianus and P. goodei. 

 Living examples of these two species are hard to come by, but it is 



■^ The first P. nelsoni recorded were found by Lieut. Nelson in a cave at 

 Ireland Island, at the other end of the islands. 



^ It is sometimes said to be a bit of surviving jungle of the ancient Bermuda. 



