The typification of the names Agave convallis Trelease and A. dissimulans Trelease is discussed and clarified. We show that the two Trelease 4 specimens associated with the name A. convallis are not duplicates (they have different collecting dates). The Trelease 4 specimen dated 5 February 1905 (barcode MO-1128755; MO specimen number 3346866) is the lectotype of the name A. convallis, while the other Trelease 4 specimen dated 12 February 1905 (barcode MO-1256267; MO specimen number 3346867) is a syntype. We confirm the lectotypification of the name A. dissimulans, with one of the two Trelease 81 specimens dated 11 February 1905 (barcode MO-1128757; MO specimen number 3346870). The other Trelease 81 specimen, which is also dated 11 February 1905 (barcode MO-1128758; MO specimen number 3346869), is an isolectotype. The typification status of Trelease 82, which is also dated 11 February 1905 [barcode MO-1256273; MO specimen number 3346871], is that of syntype. All the Trelease specimens mentioned here are held in the Herbarium of the Missouri Botanical Garden (MO). For the sake of completeness we also refer to the typification, and clarify the etymology, of the name Agave kerchovei Lem. This species is a close relative of A. convallis and A. dissimulans.