THE SNAIL TRIBE 3315 



climates; in dense forests, on the top of grassy downs, in valleys, fields, lanes, in 

 the arid desert, and at an elevation of some ten thousand feet both in the Old and 

 New World. 



To an ordinary observer, the members of the genus Arion (sometimes placed in 

 a separate family, Ariontda) are merely slugs. Externally the resemblance is very 

 close, but the different position of the respiratory orifice, and the presence of a 

 mucus pore at the end of the foot, readily separates this genus from Limax. 

 Besides these differences, the radula is of a different type. In Limax the breathing 

 hole is situated near the hinder end of the shield, whereas in Arionitismuch further 

 forward. In the present genus there is no internal shield-like shell, as in Limax 

 but this is represented by a few unequal calcareous particles beneath the mantle. 

 Nine species of this genus are said to occur in Britain, and of these the large A. 

 empiricorum is the commonest and best known. It is sometimes intensely black, but 

 it may be brown, red, yellow, greenish, or even white. This great variation in 

 color is unaccountable, for black and red specimens occur in the same districts where 

 the natural surroundings are practically the same. The edge of the foot, when 

 crawling, displays a yellowish or orange border crossed by closely-set black lines. 

 This species usually feed on vegetable substances, but it has occasionally been known 

 to devour earthworms. It ranges over a considerable part of Europe, and has been 

 recorded from Siberia, Corsica, and as far as Madeira. 



The genus Helix includes the true snails of the type represented by the garden 

 snail (//. aspersa}, and the edible or vine snail (H. pomatia), as it has been 

 variously named. The animal is completely retractile within its shell, and the body 

 distinct from the foot, and well protected by the spiral shell. The breathing orifice 

 is on the right side beneath the margin of the aperture of the shell. The genus 

 Helix, as understood at the present time, is much more limited than it was some 

 years ago, and the tendency of conchologists is to propose still further limitations. 

 The necessity of dividing an enormous genus like Helix containing thousands of 

 species, is universally recognized, but the danger arises of carrying this sectionizing 

 too far. Many of the divisions are partly founded upon geographical considerations. 

 The form of the shell in Helix is extremely variable, as a glance at any collection 

 will show. Some are sharply conical, others globular, or flat and acutely keeled at 

 the circumference; and the variety of color is endless, and changeable in specimens 

 of the same species. The British H. nemoralis and H. hortensis are striking 

 examples; and H. pida, a beautiful Cuban shell, is another remarkable instance. 

 Not only does the ground color offer many variations, but the color and disposition 

 of the spiral lines or bands which adorn the surface are equally variable. The 

 twenty-five species of Helix which occur in Britain are insignificant in comparison 

 with their exotic relatives, although large enough to do a considerable amount of 

 damage in the garden. The finest is the H. pomatia, popularly known as the apple 

 snail, but this name, as pointed out by various writers, although appropriate as 

 regards its shape, was not derived from the L,atin pomum, an apple, but from the 

 Greek poma, signifying a lid or operculum. When winter is approaching, the animal 

 secretes a diaphragm or covering to the aperture of the shell, a false operculum, to 

 keep out the cold and wet when hibernating under ground. It is composed of slime 



