OK, just a very general differences, but this should help you. In the pictures below, you can see all 4 species of the ventricosum complex. The petals of chlorochilon and warscewiczii stay more or less flat, and the labellum of these two species do not have a prominent pedicel (in other words, they are just attached to the flower as a whole). Cyc. warscewiczii flowers are like a star, with the petals perpendicular to the labellum, while in Cyc. chlorochilon the petals are positioned upwards "almost parallel" to the labellum.
Cyc. ventricosum and Cyc. lehmanni have petals that go backwards and labellum joining the flower via a pedicel. The pedicel in lehmannii is proportionally larger and the white part of the labellum is very rounded (almost like having hydrocephalia)
(Added later on: Cyc. lehmannii's petals are also "veined" (can be seen in the attached picture)
Cycnoches warscewiczii by
hawaiiansunshine, on Flickr
Cycnoches chlorochilon (Swan Orchid) by
aeranthes, on Flickr
Cycnoches ventricosum by
kavanaru, on Flickr
Cycnoches lehmannii by
kavanaru, on Flickr
Linear Mode
