152 GEOMITRA. 



nent fulcrum. — Obs. The wide hiatus in the ventral margins of 

 this equilateral shell prevents the possibility of confounding 

 it with any other. Four or five recent species are known, one of 

 which is found on the coast of Sicily, and also in the British 

 Channel. G. Turtoni, fig. 58. 



GALERICULUS. (Galericulum, a little cap or boDnet.) Velutina, 

 Auct. fig. 337. 



GALERUS. Humph. Calyptr^ea, Lam. 



GAPING. (Hians.) Bivalve shells are said to gape when the 

 margins do not meet all round. Ex. Gastrochsena, fig. 52. 



GARI. Schum. Psammobia, Lam. 



GASTEROPODA. Lam. (Vaarrip, gaster, belly ; ^roi/e, tto<W, 

 pus, podos, a foot.) The second order of the class Mollusca, Lam. 

 containing those molluscous animals whose organs of locomotion 

 are ventral. Most of the shells belonging to this order are 

 patelliform, placed upon the back of the animals, which rest or 

 crawl upon the belly. This order is divided into Pneumonobran- 

 chiata, that is, those which breath air, or land molluscs ; and Hy- 

 drobranchiata, or those which breath water, marine or fresh-water 

 molluscs. Fig. 227 to 263. 



GASTRANEA. Schum.? Corbula, Auct. 



GASTROCHiENA. Speng. (Taarrjp, gaster, belly ; x aiVii) > c ^ a ^ no > 

 gape.) Fam. Pholadaria, Lam. Pyloridea, Bl. — Descr. Equi- 

 valve, regular, inequilateral, with a wide, oblique, ventral hiatus, 

 enclosed in a curved pyriform tube. Differing from Galeomma in 

 being a free, oblique shell ; from Fistulana, in the oval shape of 

 the valves, and the curve of the tube; from Aspergillum and Clava- 

 gella, in both valves being free. — Obs. The Gastrochaenoe are 

 found in the hollows of massive shells or other marine substances. 

 Fig. 62, G. Modiolina. 



GASTROPLAX. Bl. Umbrella, Lam. De Blainville described 

 this genus from a specimen in which the shell had been, proba- 

 bly by accident, placed upon the under part of the animal, and 

 not discovering his error until afterwards, gave it the above name. 



GEOMITRA. Sw. A sub-genus of Geotrochus, Sw. founded on 

 a trochiform species of Helix, with coronated nodules on the 



