Elements of conchology Prepared Elements of conchology / Prepared for the use of schools and colleges elementsofconcho00rusc Year: 1844 Fig. 41. TROCHUS CONCAVUS, Fig. 42. TROCHUS IRIS. Another variety is remarka- ble for a deep excavation at the base of the columella, resem- bling an umbilicus, and a pro- jection of the circumference, as is seen in the figure of the con- cave trochiis {Jig. 41), which inhabits the Indian Seas, and is considered rare. There are other species, without an umbi- licus, conical with a very oblique base; the aperture large, slightly angular» the columella twisted
Elements of conchology Prepared Elements of conchology / Prepared for the use of schools and colleges elementsofconcho00rusc Year: 1844 Fig. 41. TROCHUS CONCAVUS, Fig. 42. TROCHUS IRIS. Another variety is remarka- ble for a deep excavation at the base of the columella, resem- bling an umbilicus, and a pro- jection of the circumference, as is seen in the figure of the con- cave trochiis {Jig. 41), which inhabits the Indian Seas, and is considered rare. There are other species, without an umbi- licus, conical with a very oblique base; the aperture large, slightly angular» the columella twisted, and forming a kind of tooth at its termination. Such is the rainbow trochus {fg. 42), the nacre of which is a beautiful golden green, with very brilliant reflections of red. 31. The tribe of Turbo comprises all the pecti- nibranch gasteropods which have a completely and regularly turbinated shell, terminated by an entirely round aper- ture In it we range the turbo properly so called, delphinula, turri- tella, scalaria, cyclostoma, valvata, &c. {fg. 43). 32„ The Turbos properly so called are recognised by their round or oval thick shell, in which the ap- erture is completed within by the whorl of the spire next to the last. These mollusks have two loner ten- o tacles, which, at their base, externally, support the pedunculated eyes; on the sides of the foot we remark membranous wings, sometimes simple,sometimes fringed or furnished with one or two filaments; and their operculum is sometimes horny, at others calcareous, or extremely thick.— Among the varieties of this genus is the Tvrho Pica {fig. 44), which inhabits the 31, What are the characters of the tribe of Turbo ? (Turbo is a Latin word, meaning a whirling or twisting.) 32 What are the characters of the Turbo properly so called?
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