44 INTRODUCTION TO CONCHOLOGY. 



the globe, inhabiting deep waters, and seklom seen except at 

 night. Some of the unclothed brotherhood possess an in- 

 ternal rudimentary shell : the Cuttle-fish [Sepia) ^ for instance, 

 has an oval plate ; the Calamary [Loligo), a long horny shell, 

 resembling a quill-pen ; and the Oii7/choteuthis, a thin oblong 

 shell, like a three-edged sword. The highly organized and 

 finned, enjoy more rapid powers of locomotion than such as are 

 encumbered with a shell, but are less adapted to find their 

 home in very deep water. The Sejna is less protected than 

 many others against the attacks of his enemies ; but then he 

 is provided with a mode of self-defence which the well- 

 armed Nautilus does not possess. He carries with him a small 

 bag full of black, inky fluid, and when danger approaches he 

 darkens with it the surrounding water. Thus enabled to 

 elude the vigilance of his pursuers, he readily escapes ; while 

 the baffled foe is suddenly enveloped in a darkness deep as 

 midnight. Proteus-like, he has other means of escape, and 

 often may the wily creature be seen changing colour, after 

 the manner of a chameleon, and bewildering his enemy, when 

 in hot pursuit, by the strange aspect wliich he instantaneously 

 presents. 



Others of the same family are also provided with ink- 

 bags ; but in these a considerable difference exists. Such as 



