63 



HELICnXE. 



HELICID^E. 



Aquatic. 



Tentacles contractile. 

 Trachelipodous (mantle thick-edged). Aurkididce. 

 Trachelipodous (mantle thin-edged). Limnieadue. 

 Gasteropodoua (mantle shield-like). Onchidiadce. 



With regard to the arrangement, Dr. Gray has since corrected 

 that of the first division, because the distinction between the first 

 two families, though it is that used by Lamarck, Cuvier, and others, 

 ia, in his opinion, artificial, and of little importance ; and the know- 

 which he has since acquired of the animals of several genera 

 which were before unknown, have shown him that the character 

 which De Fdrussac pointed out as the distinction between Arion 

 uiid Limiu; (but which many succeeding naturalists have considered 

 of little importance) is even of more importance than was accorded 

 to it by De Ferussac, affording a good character for dividing the 

 Land Pulmonobranchous ifollusca into two families. Thus, he 

 observes, the Arionidte are characterised by having a gland on the 

 end of the tail (which, in the gasteropodous genera, is produced 

 beyond the mantle), and they have the orifices of the organs of 

 generation on the right side immediately under the respiratory 

 hole ; whilst in Helicida; there is no gland on the end of the tail, and 

 the orifice above referred to is just behind the base of the upper right 

 tentacle. There is also, he states, an important difference in the 

 nervous system between the two families : in the first, the under part 

 of the infra-gular ganglion is 6-lobed, whilst it is only 4-lobed in the 

 iilie. Dr. Gray is further of opinion that at present only a few 

 genera, as Anon and 2/tlicarim, F5r., Nanina, Gray, and Sttnopui, 

 Uuikliiifr, can be referred with certainty to the Arionidcc; but he 

 thinks it very probable that, when the animals of other sheila are 

 known, many of them may be found to belong to that family. 



Geographical Distribution and Habits. The IleLicida: are most widely 

 diffused over the surface of the earth ; acarcely any countries but 

 those where the climate is surpaasingly rigorous are without some 

 species of the family. Many of the shells are strikingly beautiful in 

 form and colour, and these are mostly the inhabitants of intertropical 

 countries. Some of the genera (Achatina, for instance) attain a very 

 large size, and lay eggs in proportion. Helix aiperia, the common 

 11 Snail, is distributed over a large portion of the globe. It is 

 found, for instance, at the foot of Chimbomjo, in the forests of Guyana 

 and Brazil, and on all the coasts of the Mediterranean in Europe, Asia, 

 and Africa. Helix Pomutia has been naturalised with us, and is still 

 found in some countries. The first importation is attributed by some 

 to Sir Kenelm Digby. Merrett mentions it as a British inhabitant 

 before his time. A moist and rather warm state of the atmosphere 

 seems most congenial to this family. To avoid great dry heat they 

 get under stones, under old trunks of trees, leaves, &c., and some of 

 the species will burrow into the earth for protection against it. A 

 shower will bring them forth in such numbers sometimes, the smaller 

 species especially, as to induce the belief in some cases that it has 

 been raining sn.-iils. Most of the species hybernate. 



Utility to Man. The /ftlicidce, from their voracity, are very injurious 

 agriculturist and horticulturist ; but there can be no doubt 

 that tin; larger species are good food. We know that they were a 

 fiiviiuritt! di. j h with the Romans, who bad their ' Cochlearia," where they 

 were regularly fattened with new wine boiled down and meal (sapa et 

 farre, &c.) (Pliny, 'Hist.,' lib. ix. c. 56.) Jlelix Pomatia is used aa 

 food in many parts of Europe during Lent, and the snails are kept in 

 an escargotoire (snaillery), which is generally a large place boarded in, 

 having the floor covered half a foot deep with herbs, where the 

 animals fatten. Many are familiar with the passage in Pliny (loc. cit. ), 

 who, on the authority of Varro, relates the incredible size to which 

 the art of fattening had brought the snails. There must, one should 

 think, be some mistake in the text, which says " Cujua artis gloria 

 in earn magnitudinem perducta sit, ut octogiuta quadrantes caperent 

 xin/nlarum calices." Pennant, referring to this and to Varro ('De 

 It- ll'istica'), says, "If we should credit Varro, they grew so large 

 that the shells of some would hold ten quarts ! People need not 

 admire the temperance of the supper of the younger Pliny (' Epist.,' 

 lib. i. ; Epist., xv.), which consisted of only a lettuce a-piece, three 

 snails, two eggs, a barley cake, sweet wine and snow, in case his snails 

 bore any proportion to those of Hirpinus." 



The following cuts, and those given under BfMMi/i.rs and BULIMUS, 

 will iillurd the reader an idea of some of the forms of the Hdirida : 



/'".''", Anostoma, Carocolla, Clatuilia, Strcptauci*, Balea, Vertiyo, 

 C'ycloftoma. 



rt, Cnrocolla albifabris ; I, Pupa Vva ; c, Pupa Chrys'ilif, with the unimul. 



XAT. HIST. DIV. VOt. IIL 



farlula Aiutralii. 



a, Ulatta(lia Mucuicar (ntit ; b, the same, broken, to show the chiupimn, c. 



If 



