GASTEROPODA. 



131 



partitions, but secretes a compact calcareous matter, which 

 reaches to the very summit of the spiral part ; so that in 

 an old specimen the posterior part of the shell presents a 

 solid mass. One species only, Magilus antiquus, is known; 

 the colour is white, more or less pure, owing to the shell 

 being hid from the light by the coral which it inhabits. 



This curious shell is found in the coral known by the 

 name of Meandrina phrygia, which is a native of the Red 

 Sea. Mr. Sowerby asserts that the tube sometimes reaches 

 the length of three feet; the same writer mentions two 

 species, M. antiguus, figured above, and M. elipticus. 



Siliquaria. Brug. (Anguinaria Schum.) — Shell tu- 

 bular, irregularly spiral, like Vermetus, 

 but the tube has a continued longitudinal 

 slit ; operculum horny. Animal, with a 

 very small head, the eyes at the base of 

 the small tentacula ; the foot is like that 

 of Vermetus, cylindrical, lengthened be- 

 yond the head, and bearing an oper- 

 culum, which entirely closes the shell ; 

 between the head and the operculum is 

 the rudiment of afoot; the mantle is cloven 

 on the right side. — 7 species ; also fossil. 



This singular shell is often found in 

 sponges in the Mediterranean, and swqvm™ anguma. 

 Australian seas. The longitudinal slit is 

 supposed to be for the passage of the branchia of the 

 animal. 



Family 25.— C (EC ACE A. 



The eyes of the animals forming this family are placed 

 on the head, between, or rather behind, the base of the 

 tentacula, which are simple ; the foot is short. The shell 



K 2 



