Holotype: "Male holotype, female allotype, 5 male paratypes, and 3 female paratypes collected in wet pitfall traps placed near a gravel wash 6 miles N. of Boone, Colorado, USA, 20 May - 20 June 1976 by Jack Brookhart (deposited at DMNH)" (Brookhart & Cushing, 2002, p. 91).

Etymology: "From the latin cornu (horn) a description referring to the large horn-like setae on the dorsal surface of the male chelicera" (Brookhart & Cushing, 2002, p. 91).

Chelicerae Description: "Fixed finger undulate with a small denticle near apical end. Mesal groove obscure. Movable finger with small PT and slightly larger AT. A small IT anterior to PT and separated by a small notch below PT. No fond visible ectally, fond greatly reduced mesally with two tiny teeth. Flagellum complex typical of branchi group with flattened striate setae dorsally, apical plumose bristles distinct except the apical bristle which is strongly hooked and blunt tipped, ventral bristles also strongly plumnose. Several horn-like setae on the dorsal aspect of the chelicera (Figs. 23 & 24)" (Brookhart & Cushing, 2002, p. 91).

Operculum Description: "Genital operculum typical of the branch group with two joined, raised, rounded, pear-shaped plates surrounding the genital opening. These plates are expanded laterally at the posterior edges, with a slight notch on the truncated posterior margin (Fig. 29)" (Brookhart & Cushing, 2002, p. 93).

Diagnosis: "This species is placed in the Hemerotrecha branchi group (Muma 1951) based on the structure of the male flagellum complex and the male cheliceral profile which has modified but identifiable teeth on the male fixed finger. Females have the characteristic pear-shaped, raised operculum with a longitudinal rather than transverse genital opening. It appears most closely related to H. sevilleta, new species, H. maranthoni Muma 1962 and H. milsteadi Muma 1962 known from Texas (Muma 1962, 1970). It is easily identified by the tiny denticles of the male fixed finger, lack of fondal teeth, slightly flatter, wider, shorter ctenidia, and truncated, notched posterior edge of female genital operculum" (Brookhart & Cushing, 2002, p. 91).

Remarks: "The entire type series was collected in wet pit fall traps placed in a gravel wash populated with widely spaced salt bush, Atriplex canescens. Brookhart (1972) collected in this area but did not record this species in Colorado, probable because he used dry pit fall traps. Brookhart has also collected this species in wet traps near Peyton Road, El Paso County, Colorado. Brookhart (1972) recorded another member of the branch group, H. minima Muma 1951 from Colorado. Muma (1989) suggests that the entire group may need revision" (Brookhart & Cushing, 2002, p. 93).