Lake Lacha Lake Lacha Lake Lacha () is a freshwater lake, located in the south of Kargopolsky District of Arkhangelsk Oblast in Russia, south of the town of Kargopol. It is the largest lake in Arkhangelsk Oblast, with a surface area of and a basin area of . Lake Lacha is the source of the Onega River, one of the major waterways of the White Sea basin. The etymological origin of the name is unclear. The river basin of Lake Lacha includes the southern and western parts of Kargopolsky District of Arkhangelsk Oblast, as well as north-west of Vologda Oblast. In particular,
Onega stepanovi by an undivided zone. The surface of the undivided region of "Onega" is covered with small tubercles. "Onega" was originally described by Mikhail Fedonkin as a problematic organism, being grouped together with "Vendia", "Praecambridium" and "Vendomia" as possible stem-group arthropods due to a vague similarity with primitive Cambrian trilobites and arthropods. In 1985 Mikhail Fedonkin erected Phylum Proarticulata, in which he placed: "Onega", "Dickinsonia", "Palaeoplatoda", "Vendia", "Vendomia", "Praecambridium" and "Pseudovendia sp.", although he did not exclude the possibility that "Onega" may still be related to various lower Cambrian arthropods, such as "Skania". Andrey Yu. Ivantsov has proposed that "Onega" be