A partial left-handed spiral array of microtubules that lies generally dorsal to the main ventral disc microtubule array in Giardia species (trophozoite stage).
Comment:
Due to the asymmetric nature of the Giardia trophozoite, this term is defined spatially as the trophozoite is viewed from the dorsal side, with the two nuclei dorsal to the ventral disc, and the ventral disc toward the anterior.