MOLLUSCA OR UNIVALVES. 207 



the shell presents a solid mass. One species 

 only, Magilus antiquus, is known. The colour 

 is white, more or less pure. 



73. Leptoconchus (Ruppell). — Shell sub- 

 globular, delicate, fragile, translucent; spire 

 low, and nearly effaced by 

 the encroachment of the 

 last whorl; aperture large, 

 and in form somewhat like 

 the letter S reversed ; the 

 two margins not united; the 

 right delicate at all ages, and 

 a little expanded ; no columella or umbilicus. 

 Animal, head with a proboscis ; two tentacula, 

 with eyes in the middle ; foot moderate in size; 

 no operculum. — 1 species. 



The shell of this genus is of a dirty milk- 

 white, and is furrowed externally. It is found 

 in the Red Sea, where it is embedded in cal- 

 careous masses of Polyparia, and having no 

 communication with the water except by a mo- 

 derate opening.* 



74. Scalaria. — Shell turreted, with or 



* The descriptions of the two last genera are taken 

 from the Penny Cyclopaedia. 



