Original description of Harpagodes mexicanus by Imlay, 1940:
- "Shell large, subfusiform; spire moderate in height, probably composed of four or five whorls, but only three whorls preserved, apical angle about 45 degrees; body whorl very large, forming about three-fifths of the total height. Side of whorls of spire gently convex; ornamented with a number of indistinct spiral ribs; suture moderately impressed. Body whorl ornamented with four prominent diverging carinae whose tips project forward and outward. Middle carinae largest. Carinae separated by broader, fiat, smooth interspaces. Between the posterior carina and the suture are two weak spiral ribs. Anterior canal broken, finger-like, apparently not curved much posteriorly."
Locus typicus: Barril viejo, Coahuila State, Mexico
Stratum typicum: Barril viejo shale Member, Hauterivian, lower Cretaceous
Dimensions: Height holotype (incomplete) 110 mm.; maximum diameter 95 mm.
Holotype: Museum of Paleontology, University of Michigan no. 15976.