The Olive Shells. Rice Shells. Harp Shells 



almost to the lip by deep chocolate, banded with chestnut. At the 

 other extreme the shell is china-white, faintly mottled and banded 

 with fawn colour or violet. 



Different schemes of painting intermediate between the very 

 dark and very light forms are seen in a moderately complete 

 series of shells. These mollusks inhabit muddy sand in deep 

 water. Length, 2 to 3 inches. 



Habitat. — Ceylon and the Philippines. 



The Moor Olive (0. maura, Lam.) is one of the commonest 

 and most variable species in the genus, and one of the handsomest. 

 It may be known by the tumidity of the shell toward the depressed 

 spire, and the callosity at the posterior end of the rather wide 

 white-lined aperture. There are forms with burnt orange ex- 

 terior, faintly banded. Others are deep grayish chocolate of 

 almost solid colour. Olive forms with flame-like streaks of deeper 

 shade in broad bands are common. Lamarck's type was uni- 

 formly dark-coloured ; the streaked, zigzagged and mottled forms 

 he called varieties. The base of the columella has a tinge of red 

 in nearly all of these forms. Length, 2 to 2^ inches. 



Habitat. — Indian Ocean to Australia. 



The Tiger Olive (0. tigrina, Lam.) is smaller and broader, 

 with fine dark blue dots sprinkled thickly over an ash-coloured 

 ground. The interior is white. A dark brown form is also 

 described. 



Habitat. — East Africa to Philippines. 



The Two-plaited Olive (0. biplicata, Sby.) is a thin, smooth, 

 bluish-gray shell, its suture brown. In size and form this shell 

 is very like an olive. The blue occasionally gives way to dark 

 brown or olive; some forms are nearly white. The aperture and 

 the wide callus on the columella are violet-tinged. Two distinct 

 folds on the base of the axis justify the name. 



These little mollusks gather in companies just below the 

 level of the sand, burrowing for food with siphons at -the surface 

 for fresh water. Professor Keep says they migrate rapidly, and 

 a "school" of them is not easily located. He found them once 

 by thousands on a beach, directly after the tide had left it. He 

 says: "You must go at the very lowest morning tide, and search 

 till you find their beds. ... I took some of them home 

 and put them in a jar of beach sand and sea water. The plough- 

 shaped foot quickly digs a hole in the sand, and the long breathing- 



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