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Question
Which of the following cephalopods possesses an external shell?
Which of the following cephalopods possesses an external shell?
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Solution
The correct option is D Nautilus
Most of the molluscs are protected by a hard external shell and many of them are not mobile. Although Nautilus has an external shell, the trend in cephalopods is to internalise and reduce the shell.
Nautilidae, both extant and extinct, are characterised by involute or more or less convoluted shells that are generally smooth, with compressed or depressed whorl sections, straight to sinuous sutures and a tubular, generally central siphuncle. So, the correct answer is option C.
Most of the molluscs are protected by a hard external shell and many of them are not mobile. Although Nautilus has an external shell, the trend in cephalopods is to internalise and reduce the shell.
Nautilidae, both extant and extinct, are characterised by involute or more or less convoluted shells that are generally smooth, with compressed or depressed whorl sections, straight to sinuous sutures and a tubular, generally central siphuncle. So, the correct answer is option C.
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