Elements of conchology Prepared Elements of conchology / Prepared for the use of schools and colleges elementsofconcho00rusc Year: 1844 in the form of the animal. It has no oper- culum, but carries on its foot a substantial vesicular organ, which resembles froth bub- bles, which hinders it from crawling, but en- ables it to float on the surface of the water. Its head is in the form of a trunk, and has a forked tentacle on each side. The common ^^5^, species—Janthinafragilis—with a very thin violet-coloured shell, is very common in the Mediterranean, and the seas of all warm regi
Elements of conchology Prepared Elements of conchology / Prepared for the use of schools and colleges elementsofconcho00rusc Year: 1844 in the form of the animal. It has no oper- culum, but carries on its foot a substantial vesicular organ, which resembles froth bub- bles, which hinders it from crawling, but en- ables it to float on the surface of the water. Its head is in the form of a trunk, and has a forked tentacle on each side. The common ^^5^, species—Janthinafragilis—with a very thin violet-coloured shell, is very common in the Mediterranean, and the seas of all warm regions. Great numbers of them are frequently met with in per- fectly calm weather floating on the surface of !he ocean. When the animal is touched, itejects a deep violet-coloured liquor, which dyes the water all round it. The vesicular or froth-like buoy is about three limes the size of the animal; it is in the form of a cone, projecting from one side. 45, The Nerit^ are distinjjuished by the columella being a straight line, which makes the aperture of the shell either semi-circular or semi-ellipticaf. They are divided into Natica, in which the shell is umbilicafe {fig, 20, page 34) and the operculum horny; into Nerita^ properly so called^ in which the shell is not umbili- cate, thick {fig. 55), and the o])erculum stony, and into Neritina, in which the shell is also without an umbilicus, very Fig. 55. NERITA PELORONTAo Bleeding Tooth. thin, and the operculum is horny. The last live in fresh waters. 45. Row is the genus Neri'ta distinguished ?
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