GNATHODON. Gray. ([Greek: Gnathos], _gnathos_, jaw-bone; [Greek: odos], [Greek: odontos], _odontos_, tooth.) _Fam._ Mactracea, Lam.--_Descr._ Ovate, posteriorly angulated, equivalve, thick, ventricose, inequilateral, covered with a greenish brown epidermis; umbo distant, prominent; hinge having in one valve a sharp, angular, notched, cardinal tooth, and two lateral teeth, the posterior of which is elongated, and the anterior angulated, tortuous, shaped like a jaw-bone; in the other valve, two cardinal and two lateral teeth, the anterior of which is wedge-shaped; ligament internal, cuneiform, placed in a deep cardinal pit proceeding from the umbones; muscular impressions two; palleal impression having a slight sinus.--_Obs._ Only one species is known, G. cuneatus, fig. 83, from New Orleans. It is known from all other shells by the character of the hinge. GONIATITES. De Haan. A genus composed of species of Ammonites, Auct. in which the last whorl covers the spire and the sinuations of the septa are angulated. Fig. 480, G. striatus. GONIDOMUS. Sw. A sub-genus of Geotrochus, Sw. PUPA pagodus, Auct. Sw. p. 332. GONIOSTOMA. Sw. A sub-genus of Bulimus, thus described, "spire elongated, of few whorls; aperture contracted at each end; lips margined; the pillar curving inwards; the base slightly notched. G. erubescens, _Sw._ Zool. Journ. i. pl. 5, f. 2." Sw. p. 335. GONIOSTOMATÆ. Bl. A family belonging to the order Asiphonibranchiata, Bl. containing the genera Solarium and Trochus. GONOSPIRA. Sw. A sub-genus of Pupa, thus described, "spire perfectly cylindrical, of equal thickness, the tip obtuse, with the whorls large; aperture oval; lips thickened; pillar with or without a plait. G. polanga, _Desh._ Lesson, Voy. pl. 8, f. 8." Sw. p. 333. GRANULATED. (_Granum_, a grain.) Covered with minute grains, rough. The granulated lip of Oniscia, (fig. 409) will serve as an example. GRATELOUPIA. Moulins. _Fam._ Nymphacea, Lam.--_Descr._ Equivalve, inequilateral, sub-cuneiform, rounded anteriorly, sub-rostrated posteriorly; hinge with three cardinal teeth, a series of five or six irregular, small, diverging teeth behind the umbones, and one lateral anterior tooth in each valve; ligament external; muscular impressions two; palleal impression sinuated posteriorly.--_Obs._ This genus (Donax irregularis, Bast.) is only known in a fossil state. Fig. 102, G. Moulinsii.