THE APPLE SXAIL. 



211 



ME LAN I A 

 AMAKULA. 



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warmer parts of the world. In the southern States of North America they are numerous, and form 

 a peculiar group. 



The genus Melanin* has its whorls ornamented with strife or spines ; the outer lip 

 is sharp ; aperture oval, pointed above ; operculum sub-spiral. One hundred and sixty 

 species are distributed along the rivers of the south of Europe, India, the Philippines, 

 and Pacific Islands. 



The genus Paludomus (j)ahis, marsh ; domus, house) has a smooth turbinated or 

 muricated shell. The spire is small, and usually eroded ; operculum horny, lamellar, 

 nucleus external. The animal is like Melania, with a fringed margin to its mantle. 

 Ten species are known from Ceylon and India, It inhabits mountain streams, some- 

 times up to six thousand feet in elevation. 



The shell of Melanopsis has the last whorl elongated ; the spire is short and 

 pointed ; the aperture notched in front ; the inner lip is thickened ; the operculum is 

 sub-spiral. Twenty species of this genus are found in Spain, Austria, Asia Minor, and New Zealand. 



FAMILY XVI. PALUDINIDCE. 



The shells of this family are conical or globular, with a thick olive-green epidermis ; the aperture 

 of the shell is rounded and entire ; the operculum is horny, or shelly and concentric. The animal has 

 a broad muzzle ; the eyes are placed 011 short pedicels outside the tentacles, which are long and slender. 

 The Paludinidce inhabit fresh water in all parts of the world. The animal of Paludina has a small 



lobe on each side of its neck. It has a 



long muzzle and very short eye pedicels. 

 The shell is thin, turbinated, umbilicated ; 

 LINGUAL TEETH OF AMPULLAKiA.f (After s. P. Woodward.) the spire is produced ; the whorls are 



round and smooth. The development of 



the gill-bearing Gasteropods may be easily seen in the common River Snail (Paludina vivipard), 

 which bring forth their young alive, and whose oviducts in early summer contain young in all 

 stages of growth, some being a quarter of an inch in diameter. Embryos hardly visible to the naked 

 eye have a well-formed shell, ornamented with epidermal fringes, a foot, and operculum. The head 

 has long and delicate tentacles, and very distinct black eyes. Any one who is interested in mollusca 

 may watch this for himself, as Paludina is common in our ditches and marshy waters. Sixty 

 species are described as abundant in rivers and lakes throughout 

 the Northern Hemisphere, Africa, India, China, Manila, and else- 

 where. 



Valvata piscinalis is a little fresh-water mollusc, which has the 

 foot divided in front into two lobes. The shell is round and horny, 

 much shorter than Paludina or Bithynia. The animal deposits her 

 eggs in a little leather bag, which she hangs on stones or the 

 stems of water-plants, where they remain till they are hatched, 

 and liberated from their bag by the bursting of its rotting sides. 

 They all leave their prison in company, being united in a floating 

 mass of jelly. 



The Ampullaria, or " Apple Snail," has a globular shell with 

 a small spire. The body whorl is large and ventricose ; the oper- 

 culum is shelly; the left neck-lappet is formed into a long in- 

 current siphon ; the muzzle is developed into two long processes, like 



horns ; the tentacles are extremely long and slender. Ampullaria inhabits lakes and rivers in the 

 tropics. They retire deep into the mud in the dry season, and are capable of surviving a long drought, 

 having been known to revive after being kept for several years out of water. In Lake Mareotis, and at 

 the mouth of the Indus, Ampullarise are abundant, mixed with marine shells. Their eggs are large, 

 enclosed in capsiiles, and form globular masses. Fifty species have been described from South 

 America, West Indies, Africa, and India. 



AMPULLARIA CANALICVLATA. 



* Mdania, blackness. 



t For description of the Snail's tongue, or " odontophore " (tooth-bearer), see page 222. 



