Question: Who described a species found in a country that borders Guyana?
Context: Pará (] ) is a state in northern Brazil traversed by the lower Amazon River.  It borders the Brazilian states of (clockwise from north) Amapá, Maranhão, Tocantins, Mato Grosso, Amazonas and Roraima.  To the northwest it also borders Guyana and Suriname, and to the northeast it borders the Atlantic Ocean.  The capital and largest city is Belém, located at the mouth of the Amazon at the Atlantic Ocean and the 11th most populous city in the country. Venezuela, officially known as the Bolivarian Republic of Venezuela (Spanish: "República Bolivariana de Venezuela" ), is a country on the northern coast of South America.  It is a continental mainland with numerous islands located off its coastline in the Caribbean Sea.  Venezuela borders Guyana to the east of the Essequibo River, Brazil to the south, and Colombia to the west.  Trinidad and Tobago, Grenada, St. Lucia, Barbados, Curaçao, Bonaire, Aruba, Saint Vincent and the Grenadines and the Leeward Antilles lie just north, off the Venezuelan coast. The eastern lowland olingo ("Bassaricyon alleni") is a species of olingo from South America, where it is known from the lowlands east of the Andes in Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru and Venezuela.  It is the only olingo species found east of the Andes.  The Latin species name honors Joel Asaph Allen, the American zoologist who first described the genus "Bassaricyon". Russula campinensis is a neotropical species in the genus "Russula".  This species is highly different from most other known "Russula" species in that it has very small (2–17 mm), pleurotoid fruitbodies that develop on tree trunks in up to 2 m elevation from the forest floor.  It was described as "Lactarius campinensis" from Brazil (Amazonas) by Rolf Singer.  T.W. Henkel, M.C. Aime and S.L. Miller later found this species in tropical rainforest of the Pakaraima Mountains, Guyana, and showed with molecular phylogenetic methods that it belongs to "Russula".  Although forming fruitbodies on wood, "R. campinensis" is a root-symbiotic ectomycorrhizal species and has been observed in Guyana associated with "Dicymbe altsonii" and "D. jenzenii" trees in the legume subfamily Caesalpinioideae. Sphaenorhynchus lacteus, the Orinoco lime treefrog or greater hatchet-faced treefrog, is a species of frog in the family Hylidae.  It is a widely distributed species found in the Orinoco and Amazon basins in Venezuela, the Guianas (Guyana, Suriname, French Guiana), Colombia, Brazil, Ecuador, Peru, and Bolivia.  It also occurs in Trinidad and Tobago. Venezuela ( ; ] ), officially the Bolivarian Republic of Venezuela (Spanish: "República Bolivariana de Venezuela" ), is a federal republic located on the northern coast of South America.  It is bordered by Colombia on the west, Brazil on the south, Guyana on the east, the Dutch Caribbean ABC islands to the north and the islands of Trinidad and Tobago to the north-east.  Venezuela covers 916445 sqkm and has over 31 million (31,775,371) people.  The country has extremely high biodiversity (ranked 7th in the world's list of nations with the most number of species), with habitats ranging from the Andes Mountains in the west to the Amazon Basin rain-forest in the south, via extensive "llanos" plains and Caribbean coast in the center and the Orinoco River Delta in the east. The fauna of Bangladesh includes about 1,600 species of vertebrate fauna and about 1,000 species of invertebrate fauna based on incomplete records.  The vertebrate fauna consists of roughly 22 species of amphibians, 708 species of fish, 126 species of reptiles, 628 species of birds and 113 species of mammals.  The invertebrate fauna includes about 30 species of aphids, 20 species of bees, 178 species of beetles, 135 species of flies, 400 species of spiders, 150 species of lepidopterans 52 species of decapods, 30 species of copepods, 2 species of starfish and some species of sand dollars, sea cucumbers and sea urchins. Bangladesh's wide variety of ecological conditions, encompassing the long sea coast, numerous rivers and their tributaries, lakes, haors, baors, ponds and other forms of wetlands, lowland evergreen forests of tropical nature, semi-evergreen forest, hill forests, moist deciduous forests, swamps, and flat lands with tall grasses, has ensured the vast diversity of species found in the country.  However, the increasing population, unplanned urbanization and expansion of agriculture and industry have been significantly affecting the ecological structure of Bangladesh, leaving several species extinct and many others endangered. The lesser ghost bat ("Diclidurus scutatus") is a bat species found in northern Brazil, Colombia, Ecuador, French Guyana, Guyana, Peru, Surinam, and Venezuela. Isabelle's ghost bat ("Diclidurus isabella") is a bat species found in northwestern Brazil, Guyana, and Venezuela, and possibly Colombia.  It was discovered in October 1916 by Emilie Snethlage, and described by Oldfield Thomas in 1920. Mapeta xanthomelas is a species of snout moth, and the type species in the genus "Mapeta".  It was described by Walker in 1863, and is known from Guatemala and Venezuela.
Answer: Walker