AUXILIARY ORGANS — EPIPHRAGM. 
131 
According to ]\'I. Delacroix the epiiiliragm of Helix pomntla con- 
tains nearly three times more animal or organic matter than the shell, 
his analysis furnishing 57 '20 per cent, of organic matter, 28’()3 per 
cent, of carbonate of lime, and 14'77 per cent, of other and undeter- 
mined mineral substances. Mr. Growther, who has analysed an 
epiphragm of the same species from Faversham, found it to contain 
6‘83 per cent, of organic matter and 93'16 per cent, of inorganic 
substances. This analy.sis though differing so markedly (quantitatively 
from that of M. Delacroix agrees in showing the epiphragm of this 
species to contain consideralily more organic matter than the shell. 
Though the formation of an epiphragm is more especially a 
characteristic of the inoperculate land shells, yet many freshwater 
species in times of drought, when the streams and j)ools they inhabit 
become dried up, not only bury themselves more or less deej)ly in 
the mud, but some species of Flanorhis close the aqierture of the 
shell by a strongiy-adherent, firm, whitish ei)iq)hragm. Fl'nwrbis 
spirorbim is most addicted to the exercise of this power, and one of 
its synonyms, Planorbis leuco^toma, probably indicates its habitual 
indulgence in this habit, though other species have also been observed 
in the same condition. 
Those terrestrial species destitute of a sufficiently caqiacious externa l 
shell, within which they can retire for protection during unusually 
cold or dry weather, excavate for themselves a subten-anean chamber, 
the walls of which are rendered smooth, coherent and firm by an 
internal coating or lining of the mucous exudations of the animal. 
This mucus-lined earth chamber, within which the creature lies snugly 
ensconced in a contracted and tor})id state, may be considered as a 
qieculiar and interesting modification of the apertural epiphragm of 
the te.staceous sqiecies. 
LITERATURE. 
Adams, H. & A. — Tlie Genera of Recent ^lollusca, arranged according to 
their Organization, 1853 — 8. 
Andre, E. — Anat. et Pliys. Ancylns laeustris et Ancylus fluviatilis. — Rev. 
Suisse Zool., i., qip. 427— 461, 1893. 
Ashford, C. — Suggestions fora serial arrangement of the Variations of our 
Bauded Land Shells. — Journ. of Conch., iii., qiq). 89 — 95, 1880. 
Binney, W. G. — A Manual of American Land Shells. — Bull. U.S. Nat. 
Mus. , No. 20, 1885. 
Bourguignat, J. R. — Etude Synonymique sur les Mollusques des Alpes 
IMaritimes, jurhlies par A. Risso en 1826, Paris, 1861. 
De la Sinistrorsite des Espbces ; iu INIoitessier’s Hist. Malacol, du 
d(3part. de 1’ Herault, 1868, 
