The Shell-builders. 



typical of univalve shells, though sometimes the whorls 

 are not so plainly discernible. 



The Ladder-shells, or Wentletraps, are beautiful ex- 

 amples of spire-shaped shells, thick and smooth, and made 

 up of many distinct whorls, each whorl being crossed with 

 several raised ribs running from the top to the bottom 

 of the shell. The little builder of such a graceful house 

 lives in deep water, where the sea floor is rather a mix- 

 ture of sand and mud, and when disturbed is said to 

 squirt out a jet of purple fluid. One of these Wentle- 

 traps, living in Tropic seas, is a beautiful pale yellow, 

 with ribs of pure white, and for many years commanded 

 a high price amongst collectors. In 1753 four sold for 

 75, i2s., while one, which was sold a little later, was 

 valued at 27. Nowadays specimens are more numer- 

 ous, and can be purchased for a few shillings. 



In the " Pelican's Foot " shell we find the little 

 Mollusc that forms it departing from the perfect spiral 

 shape ; for although the upper part consists of a series 

 of diminishing whorls, the lip of the shell is very large, 

 flattened on one side, and spreads out like the webbed 

 foot of an aquatic bird from which the shell has gained 

 its popular name. In colour this strangely shaped shell 

 is a pale creamy yellow, sometimes nearly white, daintily 

 clouded with tender purplish tints, with here and there 

 a splash of chestnut-brown ; while the whorls are 

 sculptured with bosses and indentations. 



The Trochus, the Mollusc which forms the so- 

 called " Top-shell," is a dainty little creature with a 

 well-shaped head bearing a pair of slender horns or 

 tentacles, and a pair of eyes mounted on foot-stalks. 

 On each side of the head is a large lappet, part of the 

 (i,9io) 23 C 



