ANOMIA. 255 



the Mediterranean and Northern seas. Their shells are 

 generally thin and semitransparent^ — peculiarities rarely 

 discoverable in such as inhabit the wide ocean^ — and they 

 evince in their construction both an inconvenience and a 

 compensation. But in order to remedy this peculiarity, or to 

 prevent such fragile shells from being injured by the violent 

 tossings of the waves, a small perforation is obvious near 

 the beak, and through this a strong ligament, as already 

 noticed, is protruded, whereby the little sailor securely fixes 

 himself to marine substances, such as fuci and crabs, the 

 spines of Echini, and especially to the Maclrepora prolifera. 



The shells are various, and many of them are singularly 

 beautiful. The Snake-head, when seen in profile, resembles 

 an antique lamp, and tlie A.psittacea is very similar to the 

 recui'ved beak of a parrot, while the Cake Anomia is capable 

 of being rendered transparent by the ingenious Chinese, 

 who use it as a substitute for window-glass. 



"VYe have spoken elsewhere, and more at large, concerning 

 the prismatic arrangement of the carbonate of lime in shells. 

 The Anomia ephijopium, when submitted to a high magnifier, 

 presents a beautiful example of this arrangement in a variety 

 of tubes, which seem to commence from the inner surface of 

 the shell, and pass towards the exterior. The membranous 



