This is the Douroucouli or Cusi-cusi of the Cassiquiare which I have elsewhere described as the _Simia trivirgata_,[IM] from a drawing made by myself of the living animal. We have since seen the nocturnal monkey living in the menagerie of the Jardin des Plantes at Paris.[IN] Spix also met with this remarkable little animal on the Amazon River and called it _Nyctipithecus vociferans_. POTSDAM, JUNE 1849. HYPSOMETRIC ADDENDA. I am indebted to Mr. Pentland, whose scientific labours have thrown so much light on the geology and geography of Bolivia, for the following determinations of position, which he communicated to me in a letter from Paris (October 1848), subsequent to the publication of his great map. Nevado of Sorata, South Latitude. Longitude. Height. or Ancohuma. South Peak 15° 51′ 33″ 68° 33′ 55″ 21,286 North Peak 15° 49′ 18″ 68° 33′ 52″ 21,043 Illimani. South Peak 16° 38′ 52″ 67° 49′ 18″ 21,145 Middle Peak 16° 38′ 26″ 67° 49′ 17″ 21,094 North Peak 16° 37′ 50″ 67° 49′ 39″ 21,060 The numbers representing the heights are, with the exception of the unimportant difference of a few feet in the South Peak of Illimani, the same as those in the map of the Lake of Titicaca. A sketch of the Illimani, as it appears in all its majesty from La Paz, was given at an earlier date by Mr. Pentland in the Journal of the Royal Geographical Society.[IO] But this was five years after the publication of the first measurements in the _Annuaire du Bureau des Longitudes_ for 1830, p. 323, which results I myself hastened to disseminate in Germany.[IP] The Nevado de Sorata lies to the east of the village of Sorata or Esquibel, and is called in the Ymarra language, according to Pentland, Ancomani, Itampu, and Illhampu. In _Illimani_ we recognize the Ymarra word _illi_, snow. If, however, in the _eastern_ chain of Bolivia the Sorata was long assumed to be 3962 feet, and the Illimani 2851 feet too high, there are in the western chain of Bolivia, according to Pentland’s map of Titicaca (1848), four peaks east of Arica between the latitudes 18° 7′ and 18° 25′, all of which exceed Chimborazo in height, which itself is 21,422 feet. These four peaks are:— English feet. French feet. Pomarape 21,700 20,360 Gualateiri 21,960 20,604 Parinacota 22,030 20,670 Sahama 22,350 20,971