ST. VINCENT, CAPE VERDE ISLANDS. 47 



» 



Island is of several colours, white, bright pink or cream colour, 

 and is mainly composed of two species, of Lithothammion, 

 L. polymw-phv/rn and L. mamillare. The incrustation assumes 

 very varied forms, being simply incrusting, and following the 

 form of the rock surface on which it rests, or forming smooth 

 rounded convex masses, or being covered with a close set series 

 of projections, sometimes of considerable length, and with a 

 sinuous arrangement. 



I broke off specimens from the mass with my geological 

 hammer. It is bored in all directions by Mollusks, such as 

 Lithoclomus caucligerus — a Senegambian species with two curious 

 little tails at the hinder extremities of the valves so cut out as to 

 lap over one another when the shells are closed. On the whole, 

 plant-life seems to play a far more important role than do corals 

 in accumulating carbonate of lime around the Cape Yerdes. 

 The principal role in this respect is however played by the larger 

 Forarainifera, of the shells of which the calcareous sand of 

 St. Vincent is mainly composed. 



I made excursions every day along the shore or over the hot 

 sandy plains or over the sharp and rugged lava, in search of 

 plants and animals. So desolate is the place that a naval 

 schoolmaster, who had come to St. Vincent to join the 

 " Challenger," got lost on one of the mountains just before 

 the arrival of the ship, and died of exposure. His body was 

 found only after the lapse of several months. 



On a visit to Bird Eock, I found that the sea birds' dung 

 forms there, as at St. Paul's Eocks, pendent stalactite-like masses. 

 The rock is composed of volcanic conglomerate and tuff, traversed 

 in all directions by dikes of hard almost obsidian-like lava. Small 

 rock pools at a short distance above the waves were filled with 

 solid salt evaporated out from the spray. On the main island, 

 on the windward side, the shore rocks are covered high up with 

 an incrustation of salt dried out from the spray blown up by the 

 trade wind. Men-of-war use Bird Eock occasionally as a target, 

 and there were plenty of broken shot and shell upon it. 



At low tide, along the shore of the main island, numerous 

 rock pools were exposed at low tide. These are inhabited by 

 vast numbers of sea urchins (Echinometra) which rest within 



