3316 THE MOLLUSKS OR SHELLFISH 



and calcareous matter, but is not pierced with a minute breathing hole, as is the case 

 in some other species, although probably sufficiently porous to permit of whatever 

 change of air may be necessary during the winter sleep. The eggs of H. pomatia 

 are deposited in June in holes in the ground, formed by the snail itself. They are 

 about the size of a small pea, and much resemble in color and consistency the berries 

 of the mistletoe. Only a day or two is occupied in the production of sixty to eighty 

 eggs, and these are then covered up with earth and the ground so leveled that the 

 place, or egg nest, is difficult to discover. The length of time before hatching 

 varies according to locality and the state of the temperature. It may be from about 

 twenty to forty days before the young snail eats through the skin or shell of the 

 egg, and this it is said to entirely consume. Although H. pomatia is commonly 

 styled the edible snail, it should be remembered that other species are also con- 

 sidered a delicacy; H. aspersa, H. naticoides, and H. vermiculata being commonly 

 eaten in parts of Italy and Sicily, while in Naples, H. ligata and//! lucorum are also 

 to be seen for sale. H. mazzullii, which is collected near Palermo, possesses the 

 power of boring into the rocks; this being probably effected by means of the radula. 

 The supposed object of these excavations is to secure a place of refuge during the 

 period of excessive heat, and also to obtain a supply of lime for the formation of the 

 shell. The Philippine islands are the home of a beautiful genus of snails (Helico- 

 styla), many of which are clothed with a peculiar periostracum, which, when wetted, 

 becomes more or less transparent, disclosing the color of the shell beneath. Two 

 or three of the species are of a bluish tint, a color not found among other land 

 shells. 



The important genus Bulimus (now abolished in favor of Strophocheilus} 

 formerly contained a large number of species from all parts of the world, but is 

 now limited to a comparatively few forms occurring in South America; 6*. oblongus 

 being one of the commonest and best-known species. Another, S. maximus, is 

 sometimes as much as six inches in length. The majority of the other species, 

 originally classed in Bulimus, are now located in Bulimulus and its sections, or in 

 Buliminus. These genera are distinguished by differences of the jaw and radula. 



There are several other families of land shells, which can only 

 Other Families , , . n . , ^ ,. , ., , 



be briefly referred to. The Cyhndrelhdce are very elongate, many- 



whorled shells, which occur principally in the West Indies and South America; 



many of them being remarkable for their slender forms and exquisite 



sculpture. A peculiarity of Cylindrella consists in the shell being 



almost invariably truncated, that is, the upper whorls are broken off 



when the animal reaches maturity. This may be done to lighten the 



shell, which otherwise would be too long for the mollusk to carry 



erect. The Pupida comprises a number of forms which are concholog- 



ically very dissimilar. The typical Pupa includes minute creatures, 



and appears to be found in all parts of the globe, but especially in > ~^. 



temperate and mountainous regions. They are gregarious and live in 



moss, under stones, in the crevices of old walls, or among the roots of grass and 



other plants. Most of the species have what are called ' ' teeth ' ' within the aperture 



of the shell, and these in some species are so numerous as to almost close the 



