APPENDIX. 125 



The animal piogressfis by alternately advancing one side of 

 the foot, while the other is adherent. 



Genus XIL— ACME. 



Animal with a spiral body, placed in the centre of the foot, 

 which is elongated, and covered by a thin mantle with a thick- 

 ened margin ; tentacles two, long and slender, with eyes situate 

 near the inner side of their base. 



Genus XIII.— SUCCINEA. 



SUCCINEA AMPHIBIA, pi. XXIV, f. 22. 



Animal with a large gelatinous foot, with four short ventri- 

 cose tentacles ; body oblong, spiral, placed diagonally on the 

 superior portion of the foot. — Eggs of S. amphibia, f. 36, 37. 



Genus XIV.— ACHATINA. 



Animal with an elongated foot, on which is placed a long, 

 slender, spiral, central body ; tentacles four, the upper ones 

 subulate, obtuse, and eyeless. 



Genus XV.— BULIMUS. 



Animal with an elongated foot; body central, long, and slen- 

 der : tentacles four. 



Genus XVI.— BALNEA. 

 Animal like Bulimus, but is heteroclitical, or reversed. 



Genus XVII.— CLAUSILIA. 



Clausilia bidens, pi. XXIV, f. 28. 



Animal hke Buhmus, but reversed, or heteroclitical. 



Genus XVIII.— PUPA. 



Animal like Bulimus, with four daviform tentacles, the lower 

 pair short, and small. 



