Part 38

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.

HELICINA. Lam. Fam. Colimacea, Lam. Ellipsostomata, Bl.--Descr. Globose, compressed, or angulated, generally light and thin; aperture trigonal or semilunar; outer lip thickened and generally more or less reflected; inner lip spread over the body whorl, frequently callous near the columella, which is short, and terminates in a notch, angle, or slight callosity.--Obs. This genus of land shells, distinguished from the genus Helix, by having an operculum and a thickened columellar lip, differs also from Cyclostoma in having the aperture semicircular or angular, the peritreme discontinuous and the operculum concentric. These shells are generally small in size, and simple in form. Lamarck describes only three or four species. Mr. Gray described some others in the Zoological Journal, and in a work shortly to be published by the author, a monograph of the genus will contain descriptions and figures of at least 60 distinct species; some of which have been lately brought to this country by Mr. Cuming from the Philippine Islands. They mostly belong to tropical climates.

HELICITES. Bl. Part of the genus NUMMULITES, Lam. ROTALITES and EGEON, Montf.

HELICOGENA. Fer. A sub-genus of Helix, consisting of species, which, like the common garden snail, fig. 268, are globose and simple in form.

HELICOLIMAX. Fer. VITRINA, Drap. H. Pellucida, fig. 263.

HELICOPHANTA. Fer. A sub-genus of Helix, consisting of ear-shaped species with large open apertures.

HELICOSTYLA. Fer. A sub-genus of Helix, consisting of species with numerous whorls, as H. Epistylium, fig. 281.

HELISOMA. Sw. A sub-genus of Planorbis. Sw. p. 337.

HELIX. Auct. Fam. Colimacea, Lam.--Descr. Orbicular, light, generally globular; spire short, last whorl ventricose, aperture oblique, peritreme reflected, interrupted by the most prominent part of the body whorl; columella confluent with the outer lip, and contiguous to the axis of the shell. No operculum; a thin epidermis.--Obs. The land shells composing this genus are found in all parts of the world; the common snail, H. Aspersa, is well known as a destructive animal in our gardens. The genera Helix, Achatina, Bulinus, Clausilia, Anostoma, &c., have been united under one generic name by De Ferussac, and again divided under the following sub-generic names, each of which we shall illustrate by a figure. GENUS HELIX: Sub-genus 1, Helicophanta, consisting of species with large apertures, like Vitrina; Helix brevipes. S. gen. 2, Cochlohydra, Succinea Amphibia, Drap. S. gen. 3, Helicogena, consisting of the common species with the last whorl large; Helix Hæmastoma, H. Contusa, (Streptaxis, Gray,) H. Aspersa. S. gen. 4, Helicodonta, consisting of species with teeth or folds on the columella; Polydonta, Montf. Anostoma, Helix Nux-denticulata. S. gen. 5, Helicigona, Carocolla, Geotrochus. S. gen. 6, Helicella, consisting of depressed species with a large umbilicus; H. Citrina (Naninia, Gray.) S. gen. 7, Helicostyla, consisting of species with a simple aperture, like the Helicogenæ, but with the whorls increasing very gradually; H. epistylium. S. gen. 8, Cochlostyla, Bulinus. S. gen. 9, Cochlitoma, Achatina. S. gen. 10, Cochlicopa, Polyphemus Glans. S. gen. 11, Cochlicella, Bulinus decollatus. S. gen. 12, Cochlogena, Azeca tridens. S. gen. 13, Cochlodonta, Pupa Uva. S. gen. 14, Cochlodina, Clausilia macascarensis, Balea fragilis. The last three sub-genera are included in the genus Odostomia of Fleming. We give an example of each of these sub-divisions, for the sake of presenting the reader with the principal variations to which the genus is subject. The established genera will be characterized in their places. Fig. 254 to 281.

HELIXARION. Fer. VITRINA, Drap. Differing from Helicolimax in the structure of the animal. Fig. 262.

HEMICARDIUM. Cuv. ([Greek: hêmisus], hemisus, half, [Greek: Kardia], cardia, heart.) CARDIUM Hemicardium, fig. 123**, and several similar species.

HEMICYCLA. Sw. A sub-genus of Helix.

HEMICYCLONOSTA--see CARDILIA.

HEMICYCLOSTOMATA. Bl. The fourth family of Asiphonibranchiata, Bl. described as "more or less globular, thick, flattened on the under side; spire very short; aperture large, semilunar, entire; its outer edge hollowed; its inner or columellar edge straight, sharp and septiform." This family answers to the genus Nerita of Linnæus, and to the family Neritacea of Lamarck. It contains the genera Natica, Nerita, Neritina, and Navicella.

HEMIMACTRA. Sw. A sub-genus of Mactra, thus described: "General form of Mactra; but the cardinal teeth entirely wanting; cartilage internal, central, in a large triangular cavity; lateral teeth 2/1, distinct, lateral, striated: connected to the Glycimeri. H. gigantea, Lam. v. 472. No. 1. grandis, Sw. Sp. Nov." Sw. p. 369.

HEMIMITRA. Sw. A sub-genus of Paludomus, Sw. (Melanianæ.)

HEMIODON. Sw. A sub-genus of Anodon, described as having "Tubercles or undulations on the hinge margin. H. undulatus, purpurascens and areolata."

HEMISINUS. Sw. A sub-genus of Melania, thus described: "General shape of Melania; but the base of the aperture is contracted and emarginate; outer lip crenated. H. lineolata, Griff. Cuv. xii. pl. 13. fig. 4."

HEMITOMA. Sw. A sub-genus of Emarginula, thus described: "Patelliform; the fissure not cut through the shell, but merely forming an internal groove. H. tricostata, Sw. Sow. Gen. fig. 6."

HEMITROCHUS. Sw. A sub-genus of Geotrochus, Sw. H. hæmastoma. Sw. p. 331.

HEPTALASMIS. Leach. ([Greek: Hêpta], hepta, seven; [Greek: elasma], elasma, plate) A small shell resembling Pentelasmis, from which it differs in the number of valves, being composed of seven valves according to Leach, and of eight according to Gray, who counts the dorsal valve, which is jointed, as two, and names his genus Octolasmis. Fig. 41, H. Warwickii.

HERCOLES. Montf. A microscope shell, appearing from De Montfort's figure to resemble TROCHUS Imperialis in shape.

HERION. Montf. LENTICULINA, Bl. Microscopic.

HERMAPHRODITA. Bl. The third sub-class of Paracephalophora, Bl. divided into, Sect. 1, symmetrical, containing the orders Cirrobranchiata and Cervicobranchiata; Sect. 2, non-symmetrical, order, Scutibranchiata.

HERMES. Montf. A genus composed of CONUS Nussatella, Auct. and other elongated, cylindrical, striated species. Fig. 460.