FLORA OF PORTO SANTO 



By T. D. a. Cockerell 



Porto Santo is one of the Madeira Islands, far out in the 

 Atlantic west of Northern Africa. From the mountains near 

 the eastern end of Madeira it is eas\' to see Porto Santo, less 

 than thirty miles away. The smaller island was first inhabited, 

 and there is a legend that ]\Iadeira was found because it was 

 noticed that clouds persistently hung on the western horizon. 

 The stor\- is not ver\' plausible because on any fine day the rocks 

 of Sao Laurenco, the nearest point of Madeira, are ver>' plainly 

 visible from Porto Santo. The island of Porto Santo is about 

 six and a half miles long, and three miles across at the broadest 

 point. There are several hills or small mountains, the highest 

 having an altitude of 1660 feet. The town (Villa Baleira or 

 Whale Town) is old enough to have once been the residence of 

 Christopher Columbus, whose house is still standing. The island 

 is bare and xerophytic, strongly contrasting with the greater 

 part of Madeira, which is much moister and more covered with 

 vegetation. The Avhole archipelago is volcanic and the rock\' 

 surface is extremely rough. In Porto Santo and the Eastern 

 end of Madeira there is a great deal of sand, containing in- 

 numerable fossil land shells of Pleistocene age. In former times, 

 as is clearly indicated by marine soundings, Porto Santo must 

 have been se\"eral times larger, ^-et not so large as Madeira. 

 Fragments of this former extension remain as islets, the largest 

 of which are Lime Island (Ilheo de Baixo) and the Lighthouse 

 Island (I. de Cima). These islets, though nearly all within rifle 

 shot of the main island, have peculiar snails and beetles found 

 nowhere else. Thus on the Ilheo de Cima there occurs in 

 abundance a \ery distinct and remarkable species of land snail, 

 Geomitra lurricula Lowe. This may be taken to indicate that 

 for a long period there has been great stability of level. A very 

 slight degree of elevation would ha\e connected Cima with the 

 mainland, and allowed G. turricula to pass. Avery limited de- 

 pression would have submerged the islet and destroyed the snails. 



To the naturalist Porto Santo is chiefly remarkable for the 

 extraordinary series of endemic land shells. There are 42 

 native species of helicoid mollusks, (a few now extinct,) as 



