Shell dextral, hyperstrophic, animal sinistral.
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.
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.
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.
Ampullaria, shell dextral, coiled.
Dextral g, Antero-ventral surface.
Shell bulimoid, dextral or sinistral; radular teeth, expanded at their extremities and multicuspidate.
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).
Triforis, Physa, Clausilia are examples of sinistral Gastropods, but reversal also occurs as an individual variation among forms normally dextral.