HARPA. Brug. (_Harpa_, a harp.) _Fam._ Purpurifera, Lam. Entomostomata, Bl.--_Descr._ Oval, ventricose, longitudinally and regularly costated; spire short, with rounded, dome-like whorls; aperture wide, emarginated; outer lip thickened, reflected, composing the last costa or rib; inner lip polished, spread over part of the body whorl, terminating in a point.--_Obs._ This beautiful genus of shells is so clearly defined by the regular, longitudinal ribs that adorn the external surface, suggesting the idea of a stringed instrument, that there is no danger of confounding it with any other. H. multicostata, (Buccinum costatum, Linn.) and H. ventricosa, are among the most elegant of the testaceous productions of the sea both in form and colouring; the former is rare. The recent species are not numerous, they inhabit the Indian Ocean. A fossil species occurs at Grignon, near Paris. Fig. 419, H. ventricosa. HARPAX. Parkinson. Part of PLICATULA, Auct. HARPULA. Sw. A group of shells separated from VOLUTA, Auct. thus described, "shell generally tuberculated or longitudinally ribbed; apex of the spire papillary, smooth, and in general distorted; pillar with numerous distinct plaits; the upper, small and slender, the lower, thickest and shortest."--_Type_, H. Vexillum. (Voluta, Auct.) HAUSTATOR. Montf. A genus proposed to include those species of TURRITELLA, Auct. which have angulated whorls. HAUSTELLARIA. Sw. A sub-genus of Murex, consisting of species with long canal and no spines. Murex Haustellum, fig. 396. HAUSTRUM. Humph. PURPURA, Lamarck. HELCION. Montfort. A genus composed of species of Patella, which have the apex distinctly and prominently bent forwards. _Ex._ P. pellucida, fig. 230. HELENIS. Montf. A genus of microscopic Foraminifera. HELICELLA. Fer. One of the sub-genera into which De Ferussac has divided the genus Helix, consisting of depressed species with large umbilicus, such as Helix Algira, fig. 279. Gonites Montf. HELICIFORM. Shaped like shells of the genus Helix. HELICIGONA. One of De Ferussac's sub-genera of the genus HELIX, consisting of angulated species, such as Carocolla Lamarckii, fig. 277.