SEA-SNAILS AND SEA-SLUGS. 217 



spiral band, that the whole has been likened to a necklace. 

 So it is called Natica monilifera, and monilifera means neck- 

 lace-bearing. The animal is an odd creature, whose mantle 

 laps partly over the shell, and the large foot is furnished in 

 front with a broad fold, which is turned back as a protection 

 to the head. It is herbivorous, and crops the seaweeds on 

 sandy and gravelly shores, from low-water to about ninety 

 fathoms. 



There is a very thin, ear-shaped shell, clear and fragile, 

 known as Lamellariaperspicua. It is not sufficiently capacious 

 to accommodate the whole of the animal, so parts of it have 

 to remain permanently outside ; the mantle, for instance, can- 

 not be withdrawn, and it folds over, completely wrapping up 

 the shell and hiding it from view. It is an awkward thing to 

 have your house so small that you cannot get right inside, 

 because in the sea there are so many hungry creatures always 

 roving about, and snapping up any delicate morsel that is 

 unprotected ; and even some that are protected get swallowed 

 up in like manner. But Lamellaria has learned how to make 

 up to some extent for Nature's stinginess in the matter of 

 shell-stuff. About a quarter of a century since, Giard showed 

 that Lamellaria was to be found in association with com- 

 pound ascidians, a group to which we shall call attention in a 

 later chapter. Quite recently' 1 ' Prof. W. A. Herdman, Director 

 of the Port Erin Biological Station, added greatly to the 

 interest of Giard's observation by one of his own, which shall 

 be given in his own words : 



" Lamellaria perspiaia is not uncommon round the south 

 end of the Isle of Man, and is frequently found under the 

 circumstances described by Giard ; but I met lately with such 

 a marked case on the shore near the Biological Station at 

 Port Erin, that it seems worthy of being placed on record. 

 The mollusc was on a colony of Leptoclinum maculatum, in 

 which it had eaten a large hole. It lay in this cavity so as to 



* " Conchologist," 1893. 



