132 MR. J. ROxMANES ON THE [Feb. I9I2, 



In length it is about 40 miles, and it has an average widtli of 10 

 miles. It may, I think, be taken as a very fair example of the 

 type of topography characteristic of the Pacific coast of Central 

 America. A glance at any map of this part of Central America 

 shows a very striking difference between the coast-lines of the two 

 oceans. The Atlantic shore-line is characterized by the long, 

 smooth, sweeping curves so typical of a recently uplifted coast, 

 and that this uplift has taken place is proved by the numerous 

 raised coral-reefs which form a conspicuous feature round Limon. 

 The Pacific coast, on the other hand, shows none of these 

 characters ; it is very much more irregular, with large peninsulas 

 and bays, the most striking examples being the Gulf of Nicoya and 

 the Golfo Dulce : these suggest at once that the main factor in the 

 formation of the Pacific shore-line has been submergence instead 

 of elevation. An examination of the coast-line in detail leads to 

 the same conclusion. 



There is no continuous belt of coastal swamp, such as is present 

 on the Atlantic shores, but instead there is a succession of bold 

 rocky headlands separated by curved sandy bays. These headlands 

 are the seaward termination of the mountain-ranges of the interior. 

 On the south-eastern coast of "Nicoya these ridges may easily be 

 traced for a considerable distance out into the gulf as a series of 

 rocky islets. 



That some considerable time has elapsed since this drowning 

 took place is evident from the fact that the original form and size 

 of the Gulf has been much modified by recent deposits. Two 

 main types of these may be noted : in the first place, there are 

 large deposits of beautifull}^ clean quartzose sand; while Puntarenas 

 itself, as the name implies, is built on a sand-spit. This latter 

 is about 2 miles long, only a few hundred yards wide, and 

 nowhere more than 15 to 20 feet above high-water mark. The 

 recurved form of the point is very well marked, and the formation 

 of this spit of sand is without doubt due to the strong tidal currents 

 which prevail in the Gulf. Of much greater extent and imjjortance, 

 however, are the deposits formed by the fine alluvial mud which 

 many of the rivers are continuously bringing down in great quantity, 

 even in the dry season. In this way many large areas have been 

 completely silted up, giving rise to flat alluvial land und mangrove 

 swamps, the eft'ect being to lessen to a great extent the irregularities 

 in the coast-line due to the submergence. 



Before the accumulation of this alluvium Nico} a can only have 

 been connected to the mainland by a narrow isthmus, as the llio 

 Tempisqui is tidal for a very long way above its mouth and flows 

 through mangrove swamps and alluvial flats. The whole of the 

 lower part of this valley must, therefore, have originally been a 

 long narrow area of the Gulf of Nicoya running approximately 

 north-west and south-east. A very fine example of a completely 

 silted bay is to be observed at Salinas (see PL VIII, fig. 2), a short 

 distance south-west of Puntarenas. The old shore-lines can be 

 very clearly seen in this case, rising abruptly from the wide expanse 



