'Top-shells and Pheasant-shell 



20I 



Head of Grey-top 



angular. The umbilicus is not always present, and 

 is very variable even in tlie same species. The head 

 of the animal is furnished with 

 lobes, as shown in this figure of 

 the Grey - top's head. At the 

 " tail " end of the animal an iri- 

 descent horny disk, showing a 

 spiral structure, will be seen ; this 

 is the operculum, which closes the 

 shell when the creature has retired. 



The Common Top-shell (T. zizijphinus) 

 is regularly pyramidal with an almost 

 flattened base, solid, and somewhat glossy. 

 Operculum Ridgcs of various sizes run spirally from 

 the sharp apex to the rhomboidal mouth; 

 the largest ridge being that which 

 marks the base of each whorl. The 

 p:round colour varies from flesh colour 

 to purple overlaid with interrupted 

 or zigzag streaks of dark red. There 

 are from 10 to 12 whorls in a full- 

 grown specimen. The animal is 

 yellowish, variegated with crimson, 

 brown. The prominent head has a 

 veil ; tentacles with a brown central streak ; eyes 

 large, with black pupils, on stout footstalks. The 

 side appendages are usually four pairs. The oper- 

 culum has 15 or more whorls. Like all the 

 members of the genus, the Common Top feeds 

 upon seaweeds, and it may be found in plenty in 

 the zone below low - water mark, where the great 

 wracks and oar-weeds grow. It also extends to 

 a depth of 85 fathoms, and some of the finest 



Common Top-shell 



purple, and 

 small bilobed 



