FAMILY 3. CYCLOSTOMACEA. 93 
TRUNCATELLA, Risso. 
Testa turriculata, cylindrica, apice decollato aut truncato-obtuso, anfrac- 
tibus vel levibus, vel transverse costatis ; apertura ovali, brevi, peri- 
tremate continuo ; labro simplici. Operculum ovale, subspirale. 
The genus Truncatella was proposed by Risso for the purpose of distin- 
guishing the Cyclostoma truncatulum of Draparnaud, on account of the dif- 
ference which he discovered to exist in its organization and habits. The 
foot or organ of locomotion is in the Truncatelle divided, as it were, into 
two parts, and the animal acquires motion by contracting the space be- 
tween them into the form of a loop; hence they are called by Gray the 
Looping Snails: and in habits they differ from the Cyclostomata in being 
partially aquatic, enabled to live for a considerable time under water. The 
peculiarities which entitle these mollusks to the rank of a genus were 
noticed about the same time by the Rev. R. T. Lowe, of Madeira ; for we 
are informed by that zealous naturalist in the ‘ Zoological Journal,’ that 
upon the publication of Risso’s memoir he had already distinguished 
them in manuscript by the title of Erpetometra, in allusion to their sin- 
gular manner of crawling. The Truncatelle were abundantly found by 
Payrandeau on the shores of the Mediterranean, and Michaud also disco- 
vered that they were aquatic: the first of these authors arranges them in 
his catalogue of the mollusks of Corsica with the Paludine, the latter 
places them with the Rissoe. The genus which we have adopted cannot 
fail to be appreciated, and we place it amongst the pulmobranchiate Gas- 
teropoda, presuming that the Truncateliz are amphibious, like the Suce- 
cinee, an opinion of which the following experiment recorded by Lowe is 
almost conclusive. A specimen was taken out of the water by this gen- 
tleman on the coast of Madeira, together with several other aquatic mol- 
lusks, and they were all put away together in a dry tin box; five weeks 
afterwards the box was opened, and upon placing them in a glass of sea- 
water the Truncatelle crawled forth alive, but the other mollusks were 
dead. 
