TIIM LOOl'ING SNAIL. 



393 



not very particular about this drawback, neither is the thrush, which, in winter, when 

 tile snails are hidden away in their dark recesses, finds a meal easier to be obtained 

 on the sea-shore than in hunting for its usual prey. 



OM: of the prettiest members of this family is the WINDING STAIRCASE-SHELL or 

 PKRsi'KrTivKTkornrs, so named on account of the peculiar formation of its whorls. 



If the shell be held with its top downwards, it looks exactly as if it had been wound 

 around a conical centre which had afterwards been withdrawn, and the projecting 

 ed^es of the whorls have a wonderful resemblance to the perspective view of a wind- 

 ing staircase seen from below. 





INDIAN PHORUS. 



Phorus 'ladicus. 



STAIRCASE OR PERSPECTIVE TROCHUS.- 

 Solarlum perspectlvutn. 



Perhaps the most remarkable point about this genus is the singular operculum of 

 some of the species, which differs from that of any other mollusc. Instead of being a 

 nearly flat plate of horny or shelly substance, it is a conical structure of shelly matter 

 with a ribbon of membranous substance wound round it, and projecting like the 

 mechanical form so well known as Archimedes' , crew. The object of this singular 

 variation is quite unknown. 



The color of the shell is rather variable, but consists of mottlings with brown, ochre, 

 and white. 



A VERY curious member of this family is the LOOPING ^SA.lL(TruH(atellatruncdtulo) t 

 a little species that is remarkable for the habit which has earned for it its popular 

 name. All these creatures inhabit the space between tide marks, and can live for 

 many weeks without water. Their mode of progression is very peculiar, and closely 

 resembles that of the leeches or looping geometric caterpillars with which we are so 



