130 CLASS III. GASTEROPODA. ORDER VII, PECTINIBRANCHIATA. 
allude to was made accidentally, and is related with much enthusiasm by 
Deshayes. When M. Cailliaud opened a box of Ampullariz on his return 
to Paris, he unexpectedly found, on placing them in water, that many 
were alive, although they had been confined for several months past. 
Deshayes, who was naturally surprised to find that these water-breathing 
pectinibranchiate mollusks had existed so long out of water, examined 
them more minutely; and upon the discovery of an unusual internal 
cavity, he was led to believe that they possessed the remarkable property 
of securing, by the assistance of a closely fitting operculum, a certain 
quantity of water for the purpose of sustaining respiration out of their 
natural element. The cavity, which Deshayes observed in the Ampul- 
lari, has, however, been discovered by D’Orbigny to be a distinct pul- 
monary apparatus, with which these animals are furnished in addition to 
the usual branchial cavity, in order to enable them to live for a time out 
of water. They differ essentially in this particular from the Paludine, 
for it is a change in which their system of respiration becomes subservient 
to the difference of their habits ; the Paludine live in deep lakes or run- 
ning waters, but the Ampullariz are found located in shallow marshes, 
where the water is stagnant, and occasionally dried up. 
The Ampullariz are generally provided with a long siphon for the pur- 
pose of conveying the surrounding fluid to the respiratory cavities ; the 
few that are destitute of this appendage have been separated by D’Orbigny 
under the title of Ampulloidea*. The reversed species of this genus form 
the Lanistes of De Montford ; those which have the margin of the aper- 
ture thickened are distinguished by Guilding with the new appellation of 
Pachystoma, and the same author proposes the name of Ceratodes for the 
well-known A. cornu arietis and its cognate species,—species, which, ac- 
cording to the operculoidal classification of Sowerby, would belong to 
the genus Paludina. The genus Ampullacera, instituted by Quoy for the 
reception of the Ampullaria avellana of Lamarck, may also be abandoned, - 
* Asolene and Ampulloidea, both included by Gray in his family of Ampullariade as separate 
genera, are one and the same. Asolene is a name which D’Orbigny thought of giving to this 
genus, before he decided upon that of Ampulloidea. 
