Typical glabellum appears restricted to three disjunct areas, in the Bluegrass of Ky., the Central Basin of Tenn. and a few glades in Ala. (K). Although locally common, the species is generally rare, even in Tenn. where it is most frequent (Ch+). Records from the Ozarks of Mo. and Ark. remain dubious due to confusion with arkansanum (W and citations). C. glabellum usually grows on calcareous soils in thin woods and edges of cedar glades, often disturbed by various factors, including stream scouring and rough unpaved roads. The distribution of glabellum in Ky. suggests an association with bison trails or other megafauna before settlement. It is known only from the lower Kentucky Valley in the Eden Shale Hills, where it is locally frequent (FRAN, HENR, OWEN, ?WOOD); and from scattered locations in dolomitic transitions to the southern Knobs (GARR, LINC) and western Knobs (JEFF, OLDH). But the species appears to have been uncommon even in Short's time, when he knew it as Cunila glabella: "only on the borders of a rivulet emptying into Elkhorn, at the Forks near Frankfort, Ky." (Short & Peter 1834). C. glabellum, in its strict sense, has been confused in some literature with the closely related C. arkansanum (Nutt.) House (= Hedeoma glabra Nutt., Satureja glabella (Michx.) Briq. var. angustifolia (Torr.) Svenson). The latter is reportedly more widespread across east-central states but most common in the Ozarks. It is not verified in Ky., but a coll. from GARR (EKY), made by W. Overbeck in 2011 appeared at first to be somewhat intermediate. C. arkansanas differs as follows: plant stoloniferous, bearing distinct leafy stolons with ovate leaves (versus not so); leaves of the flowering stems generally smaller, up to 10-20 x 1-5 mm (versus 25-50 x 5-17 mm), entire (versus with several teeth on each side).