PANAMIC-PACIFIG PELECYPODA 21 



while the Tumbez Rivier, rising far back in the Andes, is a permanent, 

 fast flowing stream. In the lower reaches of the Tumbez River, where its 

 waters are rendered brackish by the tide, its banks are lined with a sub- 

 stantial growth of mangrove. This is the most southerly occurrence of this 

 plant along the west coast of South America at this time. In the Pleistocene, 

 the climate or northwestern Peru was at times more humid than at present, 

 with mangrove extending at least two degrees or about 120 nautical miles 

 further south as shown by the occurrence of its fossil leaves in clay beds 

 near Talara and by specimens of Anadara grandis and A. tuberculosa at 

 Sechura, and near Lagunitas; these mollusks as shown above occur in 

 abundance only where mangrove conditions exist. During the climatic dis- 

 turbances known as the invasion of "The El Nino" or the Aguaje, mangrove 

 seedlings from the inner reaches of the Gulf of Guayaquil drift southward on 

 the current. They become stranded in lagoonal areas along the coast, take 

 root, and are established for a short time. Botanists have shown that the 

 maintainence of successful growth of mangrove is dependent upon a mini- 

 mum amount of annual rainfall even though other ecological factors are 

 favorable. 



At the mouth of the Tumbez River (Puerto Pizarro), the shore is 

 formed by a sandy beach grading into mud flats and good collecting is 

 generally obtained there. Tumbez is the type locality for many fine species 

 obtained by Cuming. Good collecting is also generally available at Zorritos, 

 especially if dredging can be done. Further west and south along the coast 

 are numerous collecting spots mentioned as locality records in Part II of 

 this work under the names: Punta Picos; Boca Pan; Caleto Mero; Caleto Sal; 

 Mancora; Pena Negra; and Cabo Verde. The location of these places 

 is shown on the Tumbez and Piura sheets of the American Geographical 

 Society 1: 1,000,000 map of South America. This section of the Peruvian 

 coast is readily accessible, being followed by the Pan-American Highway. 



Cabo Blanco at the southwest end of the Gulf of Guayaquil is the 

 most northerly member of a series of three large, bulging headlands which 

 so well characterize this part of the northwest coast of Peru, The Cabo 

 itself is a low ridge of sandstone but immediately behind it the land 

 climbs rapidly to El Alto (an oil camp) situated on a high terrace 

 plain (Talara and Mancora tablazo), a full thousand feet above the sea. 

 Cabo Blanco is a famous fishing camp for marlin and other sport fish in 

 the waters offshore. Passing southward of Cabo Blanco and its near neigh- 

 bor Restin, the shore has a nearly due south trend and is formed mainly 

 by a sand beach as far as Punta Nautilus, a small patch of sandstone rocks 

 famous for its fossil nautiloids found there in abundance, A short distance 

 further south is the oil town of Lobitos, lying in a small bay protected 

 from the south by Punta Capullana. Punta Capullana is also the north 

 boundary of the La Brea-Parinas estate of the International Petroleum 

 Company, the largest oil producing property in coastal Peru. After crossing 

 the wide, sandy stretch of the lower Parinas Valley with its green Algarroba 

 (Honey Mesquite) trees scattered along its dried-up stream channel, there is 



