84 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



by the condition of the Double Headed Shot Cays and of the Anguila 

 Islands. 



The Double Headed Shot Cays, as approached from the south, present 

 one mass of isolated rocks, islets, and islands without vegetation. Elbow 

 Cay (Plate XXXI.), the largest island of the group, is a splendid specimen 

 of the transformations to which the seolian rocks of the Bahamas have been 

 subjected. The surface of the island is deeply pitted and honeycombed 

 in all directions. Near the edge there are many blow-holes, through 

 which the spray is sent in all directions, and on the north side, where the 

 water is deepest, the action of the northers must have been one of the 

 principal causes of the wearing away of that part of the island. The 

 seolian structure of the rocks of the island could be most plainly seen. 

 At the landing to the south of the lighthouse, as well as in the deep 

 channel for landing stores cut into the rock on the north side, the strati- 

 fication so characteristic of seolian rocks was most distinct. Steaming 

 across the bank towards the Anguila Islands we found the bottom on 

 Salt Cay Bank much like that of the other Bahama Banks, with little 

 animal life but many coralline algse. We dredged a few times on the 

 way, bringing up many fragments of shells and broken Clypeastroids 

 showing the effect of the waves on this shallow plateau. The outlying 

 rocks to the northwest of the Anguila Islands could plainly be seen to 



.EOLIAN CLIFFS, SOUTH ANGUILA. 



be of seolian origin. The islands are comparatively low, the north- 

 ern and southern extremities being somewhat higher than the central 

 mass of the islands. The long stretches of low vertical cliffs forming 

 the western shore of the islands are separated by sand beaches. The 

 hills near the southern extremity on the west shore mark the highest 

 part of the islands. Opposite our anchorage were fine seolian hills from 

 forty to fifty feet in height, full of cavities and deeply honeycombed. 



