Shell dextral, hyperstrophic, animal sinistral.
In dextral Gastropods the only structure found on the topographically right side of the rectum is the genital duct.
In a dextral Gastropod the shell is coiled in a right-handed spiral from apex to mouth, and the spiral also projects to the right of the median plane of the animal.
But there are forms in which the involution is " hyperstrophic," that is to say, the turns of the spire projecting but slightly, the spire, after flattening out gradually, finally becomes re-entrant and transformed into a false umbilicus; at the same time that part which corresponds to the umbilicus of forms with a normal coil projects and constitutes a false spire; the coil thus appears to be sinistral, although the asymmetry remains dextral, and the coil of the operculum (always the opposite to that of the shell) sinistral (e.g.
Burr.- p T 9 pl.y ped.g: reversal of the cleavage planes in sinistral as compared with dextral forms. The facts, however, strongly suggest that the original cause of the torsion was the weight of the exogastric shell and visceral hump, which in an animal creeping on its ventral surface necessarily fell over to one side.
Beneath the ciliated groove is placed an elongated ganglion (olfactory ganglion) connected by a nerve to the supraintestinal (therefore the primitively dextral) ganglion of the long h, k, m, Stomach.
Ampullaria, shell dextral, coiled.
Dextral g, Antero-ventral surface.
Shell thin, dextral, with prominent spire and oval aperture; no inferior pallial lobe.
Lanceolatus obtained by the tow-net in 8 -10 fathoms, showing the asymmetry of the large lateral sinistral mouth with its ciliated margin cm and the dextral series of simple primary gill-slits (Ips-14ps).
Shell bulimoid, dextral or sinistral; radular teeth, expanded at their extremities and multicuspidate.