Charts. Serpents Mouth (Boca de la Sierpe), south entrance to Gulf of Paria, South America, northeast coast, from survey by U. S. S. Hannibal in 1931 and British surveys from 1866-1936, Trinidad I. from British colonial survey in 1920-35; chart 1963. Scale naut. m.=1.5 in., natural scale 1:50,000.